From dd422bfcb0521a245b6bab6058dbbe7b4b7d03d1 Mon Sep 17 00:00:00 2001
From: "penify-dev[bot]" <146478655+penify-dev[bot]@users.noreply.github.com>
Date: Tue, 2 Jul 2024 15:41:23 +0000
Subject: [PATCH] Generated Documentation

---
 .../com/skydoves/sandwichdemo/MainActivity.kt |  11 +
 .../skydoves/sandwichdemo/MainRepository.kt   |  22 +
 .../skydoves/sandwichdemo/MainViewModel.kt    |  35 +-
 .../sandwichdemo/MainViewModelFactory.kt      |  11 +
 .../skydoves/sandwichdemo/SandwichDemoApp.kt  |  11 +
 .../sandwichdemo/adapter/PosterAdapter.kt     |  33 ++
 .../adapter/RecyclerViewBinding.kt            |  33 ++
 .../datasource/MainDataSourceActivity.kt      |  11 +
 .../datasource/MainDataSourceViewModel.kt     |  11 +
 .../MainDataSourceViewModelFactory.kt         |  11 +
 .../mapper/ErrorEnvelopeMapper.kt             |  11 +
 .../mapper/SuccessPosterMapper.kt             |  11 +
 .../network/DisneyDataSourceService.kt        |  11 +
 .../sandwichdemo/network/DisneyService.kt     |  22 +
 .../network/KtorfitPokemonService.kt          |  11 +
 .../network/RequestInterceptor.kt             |  11 +
 .../operator/CommonResponseOperator.kt        |  33 ++
 .../operator/GlobalResponseOperator.kt        |  44 ++
 .../operator/MainOperatorActivity.kt          |  11 +
 .../operator/MainOperatorViewModelFactory.kt  |  11 +
 .../sandwich/ktor/ApiResponseExtension.kt     |  65 ++-
 .../sandwich/ktor/HttpClientExtension.kt      |  88 +++
 .../sandwich/ktor/HttpStatementExtension.kt   |  11 +
 .../ktorfit/ApiResponseConverterFactory.kt    |  22 +
 .../retrofit/datasource/DataSource.kt         |  83 ++-
 .../datasource/DataSourceTransformer.kt       |  10 +-
 .../retrofit/datasource/ResponseDataSource.kt | 161 +++++-
 .../datasource/ResponseTransformer.kt         |  55 ++
 .../adapters/DataSourceCallAdapterFactory.kt  |  22 +
 .../internal/DataSourceCallAdapter.kt         |  22 +
 .../internal/DataSourceCallDelegate.kt        |  22 +
 .../internal/DataSourceRawCallAdapter.kt      |  22 +
 .../disposables/CompositeDisposable.kt        |  36 +-
 .../datasource/disposables/Disposable.kt      |  24 +-
 .../disposables/DisposableTransformer.kt      |  20 +-
 .../datasource/executors/ArchTaskExecutor.kt  |  37 +-
 .../executors/DefaultTaskExecutor.kt          |  33 ++
 .../datasource/executors/TaskExecutor.kt      |  11 +-
 .../retrofit/datasource/ApiAbstract.kt        |  44 ++
 .../DataSourceRawCallAdapterTest.kt           |  11 +
 .../retrofit/datasource/DataSourceTest.kt     |  66 +++
 .../retrofit/datasource/DisneyClient.kt       |  22 +
 .../datasource/DisneyDataSourceService.kt     |  11 +
 .../retrofit/datasource/DisneyService.kt      |  11 +
 .../serialization/SerializationExtensions.kt  |  22 +
 .../SerializationExtensionsTest.kt            |  22 +
 .../retrofit/ApiResponseExtensions.kt         |  43 +-
 .../sandwich/retrofit/ResponseTransformer.kt  |  44 ++
 .../adapters/ApiResponseCallAdapterFactory.kt |  22 +
 .../internal/ApiResponseCallAdapter.kt        |  22 +
 .../internal/ApiResponseCallDelegate.kt       |  22 +
 .../ApiResponseDeferredCallAdapter.kt         |  22 +
 .../interceptors/EmptyBodyInterceptor.kt      |  11 +
 .../com/skydoves/sandwich/ApiAbstract.kt      |  44 ++
 .../sandwich/ApiResponseExtensionsTest.kt     |  55 ++
 .../skydoves/sandwich/ApiResponseRetryTest.kt |  11 +
 .../sandwich/ApiResponseSuspendTest.kt        |  33 ++
 .../com/skydoves/sandwich/ApiResponseTest.kt  |  77 +++
 .../com/skydoves/sandwich/DisneyClient.kt     |  11 +
 .../sandwich/DisneyCoroutinesService.kt       |  22 +
 .../com/skydoves/sandwich/DisneyService.kt    |  11 +
 .../skydoves/sandwich/ErrorEnvelopeMapper.kt  |  11 +
 .../skydoves/sandwich/MainCoroutinesRule.kt   |  22 +
 .../sandwich/NoContentExceptionTest.kt        |  22 +
 .../kotlin/com/skydoves/sandwich/Poster.kt    |  11 +
 .../sandwich/ResponseTransformerTest.kt       | 517 ++++++++++++++++++
 .../sandwich/SandwichInitializerTest.kt       |  44 ++
 .../skydoves/sandwich/SuccessPosterMapper.kt  |  11 +
 .../com/skydoves/sandwich/ApiResponse.kt      |  83 ++-
 .../skydoves/sandwich/ResponseTransformer.kt  | 345 ++++++++++--
 .../sandwich/retry/ApiResponseRetry.kt        |  22 +
 .../skydoves/sandwich/retry/RetryPolicy.kt    |  22 +-
 72 files changed, 2761 insertions(+), 117 deletions(-)

diff --git a/app/src/main/kotlin/com/skydoves/sandwichdemo/MainActivity.kt b/app/src/main/kotlin/com/skydoves/sandwichdemo/MainActivity.kt
index 000a30c..b9351f2 100644
--- a/app/src/main/kotlin/com/skydoves/sandwichdemo/MainActivity.kt
+++ b/app/src/main/kotlin/com/skydoves/sandwichdemo/MainActivity.kt
@@ -47,4 +47,15 @@ class MainActivity : AppCompatActivity() {
       Toast.makeText(this, it, Toast.LENGTH_SHORT).show()
     }
   }
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/app/src/main/kotlin/com/skydoves/sandwichdemo/MainRepository.kt b/app/src/main/kotlin/com/skydoves/sandwichdemo/MainRepository.kt
index 649c734..9b0a36a 100644
--- a/app/src/main/kotlin/com/skydoves/sandwichdemo/MainRepository.kt
+++ b/app/src/main/kotlin/com/skydoves/sandwichdemo/MainRepository.kt
@@ -25,6 +25,28 @@ class MainRepository(
   private val disneyService: DisneyService,
 ) {
 
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun fetchPostersFlow(): Flow<ApiResponse<List<Poster>>> = flow {
     val response = disneyService.fetchDisneyPosters()
     emit(response)
diff --git a/app/src/main/kotlin/com/skydoves/sandwichdemo/MainViewModel.kt b/app/src/main/kotlin/com/skydoves/sandwichdemo/MainViewModel.kt
index 7c97887..dcf5524 100644
--- a/app/src/main/kotlin/com/skydoves/sandwichdemo/MainViewModel.kt
+++ b/app/src/main/kotlin/com/skydoves/sandwichdemo/MainViewModel.kt
@@ -101,6 +101,17 @@ class MainViewModel(private val mainRepository: MainRepository) : ViewModel() {
     retrofit()
   }
 
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   private fun retrofit() = viewModelScope.launch {
     mainRepository.fetchPosters()
       // handles the success scenario when the API request succeeds.
@@ -128,7 +139,17 @@ class MainViewModel(private val mainRepository: MainRepository) : ViewModel() {
       }
   }
 
-  // Ktor example
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   private fun ktor() = viewModelScope.launch {
     val response = client.getApiResponse<PokemonResponse>("https://pokeapi.co/api/v2/pokemon") {
       contentType(ContentType.Application.Json)
@@ -148,7 +169,17 @@ class MainViewModel(private val mainRepository: MainRepository) : ViewModel() {
     }
   }
 
-  // Ktorfit example
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   private fun ktorfit() = viewModelScope.launch {
     val ktorfit = Ktorfit.Builder().baseUrl("https://pokeapi.co/api/v2/")
       .converterFactories(ApiResponseConverterFactory.create())
diff --git a/app/src/main/kotlin/com/skydoves/sandwichdemo/MainViewModelFactory.kt b/app/src/main/kotlin/com/skydoves/sandwichdemo/MainViewModelFactory.kt
index b660361..10da9ee 100644
--- a/app/src/main/kotlin/com/skydoves/sandwichdemo/MainViewModelFactory.kt
+++ b/app/src/main/kotlin/com/skydoves/sandwichdemo/MainViewModelFactory.kt
@@ -29,4 +29,15 @@ class MainViewModelFactory : ViewModelProvider.Factory {
     }
     throw IllegalArgumentException("Unknown ViewModel class.")
   }
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/app/src/main/kotlin/com/skydoves/sandwichdemo/SandwichDemoApp.kt b/app/src/main/kotlin/com/skydoves/sandwichdemo/SandwichDemoApp.kt
index 9ab4519..7bdfcea 100644
--- a/app/src/main/kotlin/com/skydoves/sandwichdemo/SandwichDemoApp.kt
+++ b/app/src/main/kotlin/com/skydoves/sandwichdemo/SandwichDemoApp.kt
@@ -56,4 +56,15 @@ class SandwichDemoApp : Application() {
     lateinit var sandwichApp: Application
       private set
   }
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/app/src/main/kotlin/com/skydoves/sandwichdemo/adapter/PosterAdapter.kt b/app/src/main/kotlin/com/skydoves/sandwichdemo/adapter/PosterAdapter.kt
index 84bbbae..6d7b95b 100644
--- a/app/src/main/kotlin/com/skydoves/sandwichdemo/adapter/PosterAdapter.kt
+++ b/app/src/main/kotlin/com/skydoves/sandwichdemo/adapter/PosterAdapter.kt
@@ -7,6 +7,28 @@
  *
  * http://www.apache.org/licenses/LICENSE-2.0
  *
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -26,6 +48,17 @@ class PosterAdapter : RecyclerView.Adapter<PosterAdapter.PosterViewHolder>() {
 
   private val items = mutableListOf<Poster>()
 
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun addPosterList(posters: List<Poster>) {
     items.clear()
     items.addAll(posters)
diff --git a/app/src/main/kotlin/com/skydoves/sandwichdemo/adapter/RecyclerViewBinding.kt b/app/src/main/kotlin/com/skydoves/sandwichdemo/adapter/RecyclerViewBinding.kt
index ed5705f..e12863d 100644
--- a/app/src/main/kotlin/com/skydoves/sandwichdemo/adapter/RecyclerViewBinding.kt
+++ b/app/src/main/kotlin/com/skydoves/sandwichdemo/adapter/RecyclerViewBinding.kt
@@ -25,12 +25,34 @@ object RecyclerViewBinding {
 
   @JvmStatic
   @BindingAdapter("adapter")
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun bindAdapter(view: RecyclerView, posterAdapter: PosterAdapter) {
     view.adapter = posterAdapter
   }
 
   @JvmStatic
   @BindingAdapter("adapterPosterList")
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun bindAdapterPosterList(view: RecyclerView, posters: List<Poster>?) {
     if (!posters.isNullOrEmpty()) {
       (view.adapter as? PosterAdapter)?.addPosterList(posters)
@@ -39,6 +61,17 @@ object RecyclerViewBinding {
 
   @JvmStatic
   @BindingAdapter("loadImage")
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun bindLoadImage(view: AppCompatImageView, url: String) {
     Glide.with(view.context)
       .load(url)
diff --git a/app/src/main/kotlin/com/skydoves/sandwichdemo/datasource/MainDataSourceActivity.kt b/app/src/main/kotlin/com/skydoves/sandwichdemo/datasource/MainDataSourceActivity.kt
index b008d0d..184853b 100644
--- a/app/src/main/kotlin/com/skydoves/sandwichdemo/datasource/MainDataSourceActivity.kt
+++ b/app/src/main/kotlin/com/skydoves/sandwichdemo/datasource/MainDataSourceActivity.kt
@@ -44,4 +44,15 @@ class MainDataSourceActivity : AppCompatActivity() {
       Toast.makeText(this, it, Toast.LENGTH_SHORT).show()
     }
   }
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/app/src/main/kotlin/com/skydoves/sandwichdemo/datasource/MainDataSourceViewModel.kt b/app/src/main/kotlin/com/skydoves/sandwichdemo/datasource/MainDataSourceViewModel.kt
index 7842b4d..dacec03 100644
--- a/app/src/main/kotlin/com/skydoves/sandwichdemo/datasource/MainDataSourceViewModel.kt
+++ b/app/src/main/kotlin/com/skydoves/sandwichdemo/datasource/MainDataSourceViewModel.kt
@@ -95,4 +95,15 @@ class MainDataSourceViewModel constructor(disneyService: DisneyDataSourceService
       disposable.clear()
     }
   }
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/app/src/main/kotlin/com/skydoves/sandwichdemo/datasource/MainDataSourceViewModelFactory.kt b/app/src/main/kotlin/com/skydoves/sandwichdemo/datasource/MainDataSourceViewModelFactory.kt
index a601545..7ec4ee3 100644
--- a/app/src/main/kotlin/com/skydoves/sandwichdemo/datasource/MainDataSourceViewModelFactory.kt
+++ b/app/src/main/kotlin/com/skydoves/sandwichdemo/datasource/MainDataSourceViewModelFactory.kt
@@ -28,4 +28,15 @@ class MainDataSourceViewModelFactory : ViewModelProvider.Factory {
     }
     throw IllegalArgumentException("Unknown ViewModel class.")
   }
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/app/src/main/kotlin/com/skydoves/sandwichdemo/mapper/ErrorEnvelopeMapper.kt b/app/src/main/kotlin/com/skydoves/sandwichdemo/mapper/ErrorEnvelopeMapper.kt
index 60d5d3e..d05a72d 100644
--- a/app/src/main/kotlin/com/skydoves/sandwichdemo/mapper/ErrorEnvelopeMapper.kt
+++ b/app/src/main/kotlin/com/skydoves/sandwichdemo/mapper/ErrorEnvelopeMapper.kt
@@ -31,4 +31,15 @@ object ErrorEnvelopeMapper : ApiErrorModelMapper<ErrorMessage> {
   override fun map(apiErrorResponse: ApiResponse.Failure.Error): ErrorMessage {
     return ErrorMessage(apiErrorResponse.statusCode.code, apiErrorResponse.message())
   }
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/app/src/main/kotlin/com/skydoves/sandwichdemo/mapper/SuccessPosterMapper.kt b/app/src/main/kotlin/com/skydoves/sandwichdemo/mapper/SuccessPosterMapper.kt
index 8dcff3d..71075e3 100644
--- a/app/src/main/kotlin/com/skydoves/sandwichdemo/mapper/SuccessPosterMapper.kt
+++ b/app/src/main/kotlin/com/skydoves/sandwichdemo/mapper/SuccessPosterMapper.kt
@@ -29,4 +29,15 @@ object SuccessPosterMapper : ApiSuccessModelMapper<List<Poster>, Poster?> {
   override fun map(apiSuccessResponse: ApiResponse.Success<List<Poster>>): Poster? {
     return apiSuccessResponse.data.firstOrNull()
   }
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/app/src/main/kotlin/com/skydoves/sandwichdemo/network/DisneyDataSourceService.kt b/app/src/main/kotlin/com/skydoves/sandwichdemo/network/DisneyDataSourceService.kt
index 092968c..8be40b6 100644
--- a/app/src/main/kotlin/com/skydoves/sandwichdemo/network/DisneyDataSourceService.kt
+++ b/app/src/main/kotlin/com/skydoves/sandwichdemo/network/DisneyDataSourceService.kt
@@ -22,5 +22,16 @@ import retrofit2.http.GET
 interface DisneyDataSourceService {
 
   @GET("DisneyPosters.json")
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun fetchDisneyPosterList(): DataSource<List<Poster>>
 }
diff --git a/app/src/main/kotlin/com/skydoves/sandwichdemo/network/DisneyService.kt b/app/src/main/kotlin/com/skydoves/sandwichdemo/network/DisneyService.kt
index b834be2..197a19f 100644
--- a/app/src/main/kotlin/com/skydoves/sandwichdemo/network/DisneyService.kt
+++ b/app/src/main/kotlin/com/skydoves/sandwichdemo/network/DisneyService.kt
@@ -23,8 +23,30 @@ import retrofit2.http.GET
 interface DisneyService {
 
   @GET("DisneyPosters.json")
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   suspend fun fetchDisneyPosters(): ApiResponse<List<Poster>>
 
   @GET("DisneyPosters.json")
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun fetchDisneyPostersAsync(): Deferred<ApiResponse<List<Poster>>>
 }
diff --git a/app/src/main/kotlin/com/skydoves/sandwichdemo/network/KtorfitPokemonService.kt b/app/src/main/kotlin/com/skydoves/sandwichdemo/network/KtorfitPokemonService.kt
index 3550dcf..f53a84b 100644
--- a/app/src/main/kotlin/com/skydoves/sandwichdemo/network/KtorfitPokemonService.kt
+++ b/app/src/main/kotlin/com/skydoves/sandwichdemo/network/KtorfitPokemonService.kt
@@ -22,5 +22,16 @@ import de.jensklingenberg.ktorfit.http.GET
 public interface KtorfitPokemonService {
 
   @GET("pokemon")
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   suspend fun getPokemon(): ApiResponse<PokemonResponse>
 }
diff --git a/app/src/main/kotlin/com/skydoves/sandwichdemo/network/RequestInterceptor.kt b/app/src/main/kotlin/com/skydoves/sandwichdemo/network/RequestInterceptor.kt
index 2313513..8ad5c94 100644
--- a/app/src/main/kotlin/com/skydoves/sandwichdemo/network/RequestInterceptor.kt
+++ b/app/src/main/kotlin/com/skydoves/sandwichdemo/network/RequestInterceptor.kt
@@ -28,4 +28,15 @@ internal class RequestInterceptor : Interceptor {
     Timber.d("$request")
     return chain.proceed(request)
   }
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/app/src/main/kotlin/com/skydoves/sandwichdemo/operator/CommonResponseOperator.kt b/app/src/main/kotlin/com/skydoves/sandwichdemo/operator/CommonResponseOperator.kt
index b7a7d3e..f9326d0 100644
--- a/app/src/main/kotlin/com/skydoves/sandwichdemo/operator/CommonResponseOperator.kt
+++ b/app/src/main/kotlin/com/skydoves/sandwichdemo/operator/CommonResponseOperator.kt
@@ -7,6 +7,17 @@
  *
  * http://www.apache.org/licenses/LICENSE-2.0
  *
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -75,4 +86,26 @@ class CommonResponseOperator<T>(
   private fun toast(message: String) {
     Toast.makeText(application, message, Toast.LENGTH_SHORT).show()
   }
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/app/src/main/kotlin/com/skydoves/sandwichdemo/operator/GlobalResponseOperator.kt b/app/src/main/kotlin/com/skydoves/sandwichdemo/operator/GlobalResponseOperator.kt
index 6459326..eebfe70 100644
--- a/app/src/main/kotlin/com/skydoves/sandwichdemo/operator/GlobalResponseOperator.kt
+++ b/app/src/main/kotlin/com/skydoves/sandwichdemo/operator/GlobalResponseOperator.kt
@@ -7,6 +7,28 @@
  *
  * http://www.apache.org/licenses/LICENSE-2.0
  *
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -76,4 +98,26 @@ class GlobalResponseOperator<T>(
   private fun toast(message: String) {
     Toast.makeText(application, message, Toast.LENGTH_SHORT).show()
   }
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/app/src/main/kotlin/com/skydoves/sandwichdemo/operator/MainOperatorActivity.kt b/app/src/main/kotlin/com/skydoves/sandwichdemo/operator/MainOperatorActivity.kt
index d3274f6..1d1a274 100644
--- a/app/src/main/kotlin/com/skydoves/sandwichdemo/operator/MainOperatorActivity.kt
+++ b/app/src/main/kotlin/com/skydoves/sandwichdemo/operator/MainOperatorActivity.kt
@@ -41,4 +41,15 @@ class MainOperatorActivity : AppCompatActivity() {
       adapter = PosterAdapter()
     }
   }
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/app/src/main/kotlin/com/skydoves/sandwichdemo/operator/MainOperatorViewModelFactory.kt b/app/src/main/kotlin/com/skydoves/sandwichdemo/operator/MainOperatorViewModelFactory.kt
index 71ff5cd..9dede3e 100644
--- a/app/src/main/kotlin/com/skydoves/sandwichdemo/operator/MainOperatorViewModelFactory.kt
+++ b/app/src/main/kotlin/com/skydoves/sandwichdemo/operator/MainOperatorViewModelFactory.kt
@@ -28,4 +28,15 @@ class MainOperatorViewModelFactory : ViewModelProvider.Factory {
     }
     throw IllegalArgumentException("Unknown ViewModel class.")
   }
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/sandwich-ktor/src/commonMain/kotlin/com/skydoves/sandwich/ktor/ApiResponseExtension.kt b/sandwich-ktor/src/commonMain/kotlin/com/skydoves/sandwich/ktor/ApiResponseExtension.kt
index aa0a1b4..2315709 100644
--- a/sandwich-ktor/src/commonMain/kotlin/com/skydoves/sandwich/ktor/ApiResponseExtension.kt
+++ b/sandwich-ktor/src/commonMain/kotlin/com/skydoves/sandwich/ktor/ApiResponseExtension.kt
@@ -1,5 +1,60 @@
 /*
  * Designed and developed by 2020 skydoves (Jaewoong Eum)
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -33,11 +88,15 @@ import io.ktor.utils.io.charsets.Charsets
 import kotlin.jvm.JvmSynthetic
 
 /**
- * @author skydoves (Jaewoong Eum)
+ * Transforms the sign-up request data to match the backend's expected format.
  *
- * Returns a status code from the [HttpResponse].
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
  *
- * @return A [StatusCode] from the network callback response.
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
  */
 public fun HttpResponse.getStatusCode(): StatusCode {
   return StatusCode.entries.find { it.code == status.value }
diff --git a/sandwich-ktor/src/commonMain/kotlin/com/skydoves/sandwich/ktor/HttpClientExtension.kt b/sandwich-ktor/src/commonMain/kotlin/com/skydoves/sandwich/ktor/HttpClientExtension.kt
index 6f36a0c..481324e 100644
--- a/sandwich-ktor/src/commonMain/kotlin/com/skydoves/sandwich/ktor/HttpClientExtension.kt
+++ b/sandwich-ktor/src/commonMain/kotlin/com/skydoves/sandwich/ktor/HttpClientExtension.kt
@@ -7,6 +7,83 @@
  *
  * http://www.apache.org/licenses/LICENSE-2.0
  *
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -330,4 +407,15 @@ public suspend inline fun <reified T> HttpClient.headApiResponse(
 ): ApiResponse<T> = headApiResponse {
   url(urlString)
   block()
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/sandwich-ktor/src/commonMain/kotlin/com/skydoves/sandwich/ktor/HttpStatementExtension.kt b/sandwich-ktor/src/commonMain/kotlin/com/skydoves/sandwich/ktor/HttpStatementExtension.kt
index 407e6b8..2242151 100644
--- a/sandwich-ktor/src/commonMain/kotlin/com/skydoves/sandwich/ktor/HttpStatementExtension.kt
+++ b/sandwich-ktor/src/commonMain/kotlin/com/skydoves/sandwich/ktor/HttpStatementExtension.kt
@@ -27,4 +27,15 @@ import io.ktor.client.statement.HttpStatement
 public suspend inline fun <reified T> HttpStatement.executeApiResponse(): ApiResponse<T> {
   val response = execute()
   return apiResponseOf { response }
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/sandwich-ktorfit/src/commonMain/kotlin/com/skydoves/sandwich/ktorfit/ApiResponseConverterFactory.kt b/sandwich-ktorfit/src/commonMain/kotlin/com/skydoves/sandwich/ktorfit/ApiResponseConverterFactory.kt
index 719c333..ac0879f 100644
--- a/sandwich-ktorfit/src/commonMain/kotlin/com/skydoves/sandwich/ktorfit/ApiResponseConverterFactory.kt
+++ b/sandwich-ktorfit/src/commonMain/kotlin/com/skydoves/sandwich/ktorfit/ApiResponseConverterFactory.kt
@@ -68,4 +68,26 @@ public class ApiResponseConverterFactory internal constructor() : Converter.Fact
       
     }
   }
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/DataSource.kt b/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/DataSource.kt
index 4d8263c..b7babb0 100644
--- a/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/DataSource.kt
+++ b/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/DataSource.kt
@@ -28,28 +28,95 @@ import retrofit2.Callback
  */
 public interface DataSource<T> {
 
-  /** combine a call and a callback to the DataSource. */
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   public fun combine(call: Call<T>, callback: Callback<T>?): DataSource<T>
 
-  /** retry fetching data few times with time interval when the request gets failure. */
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   public fun retry(retryCount: Int, interval: Long): DataSource<T>
 
-  /** observes a [ApiResponse] value from the API call request. */
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   public fun observeResponse(observer: ResponseObserver<T>): DataSource<T>
 
   /**
-   * concat an another [DataSource] and request API calls sequentially.
-   * we can determine request continuously the concat [DataSource] or stop when failed using [ConcatStrategy].
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
    */
   public fun <R> concat(dataSource: DataSource<R>): DataSource<R>
 
-  /** request API call and response to the callback. */
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   public fun request(): DataSource<T>
 
-  /** joins onto [CompositeDisposable] as a disposable. */
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   public fun joinDisposable(disposable: CompositeDisposable): DataSource<T>
 
-  /** invalidate cached data and retry counts, request again API call. */
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   public fun invalidate()
 
   /** A concat strategy for determining to request continuously or stop when the first request got failed. */
diff --git a/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/DataSourceTransformer.kt b/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/DataSourceTransformer.kt
index da62dcf..6093caa 100644
--- a/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/DataSourceTransformer.kt
+++ b/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/DataSourceTransformer.kt
@@ -19,9 +19,15 @@
 package com.skydoves.sandwich.retrofit.datasource
 
 /**
- * @author skydoves (Jaewoong Eum)
+ * Transforms the sign-up request data to match the backend's expected format.
  *
- * Changes an instance of the [DataSource] interface to the [ResponseDataSource].
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
  */
 public fun <T> DataSource<T>.toResponseDataSource(): ResponseDataSource<T> {
   requireNotNull(this is ResponseDataSource)
diff --git a/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/ResponseDataSource.kt b/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/ResponseDataSource.kt
index d84d69f..1fa73d9 100644
--- a/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/ResponseDataSource.kt
+++ b/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/ResponseDataSource.kt
@@ -16,6 +16,83 @@
 @file:Suppress("unused")
 
 package com.skydoves.sandwich.retrofit.datasource
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 
 import androidx.lifecycle.LiveData
 import androidx.lifecycle.MutableLiveData
@@ -42,6 +119,28 @@ import kotlin.coroutines.EmptyCoroutineContext
  * Support observer for the every request responses, concat another [DataSource],
  * Retry fetching data when the request gets failure.
  */
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 public class ResponseDataSource<T> : DataSource<T> {
 
   // retrofit call from the retrofit service.
@@ -121,7 +220,17 @@ public class ResponseDataSource<T> : DataSource<T> {
   public var concatStrategy: DataSource.ConcatStrategy =
     DataSource.ConcatStrategy.CONTINUOUS
 
-  /** sets value on the worker thread and post the value to the main thread. */
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   public fun postValue(value: ApiResponse<T>) {
     val postTask: Boolean
     synchronized(dataLock) {
@@ -134,7 +243,17 @@ public class ResponseDataSource<T> : DataSource<T> {
     ArchTaskExecutor.instance.postToMainThread(postValueRunnable, 0)
   }
 
-  /** sets [DataRetainPolicy] for limiting retaining data. */
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   public fun dataRetainPolicy(dataRetainPolicy: DataRetainPolicy): ResponseDataSource<T> = apply {
     this.dataRetainPolicy = dataRetainPolicy
   }
@@ -255,11 +374,17 @@ public class ResponseDataSource<T> : DataSource<T> {
   }
 
   /**
-   * if the response is successful, it returns a [LiveData] which contains response data.
-   * if the response is failure or exception, it returns an empty [LiveData].
-   * this live data can be observable from the network requests.
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
    */
-  @Suppress("UNCHECKED_CAST")
   public fun asLiveData(): LiveData<T> {
     return MutableLiveData<T>().apply {
       liveData = this
@@ -272,7 +397,17 @@ public class ResponseDataSource<T> : DataSource<T> {
     }
   }
 
-  /** enqueue a callback to call and cache the [ApiResponse] data. */
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   private fun enqueue() {
     val call = call?.clone() ?: return
     if (!call.isExecuted && compositeDisposable?.disposed == false) {
@@ -295,7 +430,17 @@ public class ResponseDataSource<T> : DataSource<T> {
   }
 
   /** emit response data to an observer when the request is successful. */
-  @Suppress("UNCHECKED_CAST")
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   private fun emitResponseToObserver() {
     if (data != empty && (data as ApiResponse<T>) is ApiResponse.Success<T>) {
       this.responseObserver?.observe(data as ApiResponse<T>)
diff --git a/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/ResponseTransformer.kt b/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/ResponseTransformer.kt
index 9b8e7cd..ace8f7a 100644
--- a/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/ResponseTransformer.kt
+++ b/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/ResponseTransformer.kt
@@ -7,6 +7,50 @@
  *
  * http://www.apache.org/licenses/LICENSE-2.0
  *
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -150,4 +194,15 @@ internal inline fun <T> getCallbackFromOnResultWithContext(
       }
     }
   }
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/adapters/DataSourceCallAdapterFactory.kt b/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/adapters/DataSourceCallAdapterFactory.kt
index 73c04ad..bd90662 100644
--- a/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/adapters/DataSourceCallAdapterFactory.kt
+++ b/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/adapters/DataSourceCallAdapterFactory.kt
@@ -67,4 +67,26 @@ public class DataSourceCallAdapterFactory private constructor() : CallAdapter.Fa
     @JvmStatic
     public fun create(): DataSourceCallAdapterFactory = DataSourceCallAdapterFactory()
   }
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/adapters/internal/DataSourceCallAdapter.kt b/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/adapters/internal/DataSourceCallAdapter.kt
index 9b23708..0c6b6d5 100644
--- a/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/adapters/internal/DataSourceCallAdapter.kt
+++ b/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/adapters/internal/DataSourceCallAdapter.kt
@@ -7,6 +7,17 @@
  *
  * http://www.apache.org/licenses/LICENSE-2.0
  *
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -38,4 +49,15 @@ internal class DataSourceCallAdapter constructor(
   override fun adapt(call: Call<Type>): Call<DataSource<Type>> {
     return DataSourceCallDelegate(call)
   }
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/adapters/internal/DataSourceCallDelegate.kt b/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/adapters/internal/DataSourceCallDelegate.kt
index d15fc7c..62020b0 100644
--- a/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/adapters/internal/DataSourceCallDelegate.kt
+++ b/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/adapters/internal/DataSourceCallDelegate.kt
@@ -7,6 +7,17 @@
  *
  * http://www.apache.org/licenses/LICENSE-2.0
  *
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -42,4 +53,15 @@ internal class DataSourceCallDelegate<T>(proxy: Call<T>) : CallDelegate<T, DataS
   }
 
   override fun cloneImpl() = DataSourceCallDelegate(proxy.clone())
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/adapters/internal/DataSourceRawCallAdapter.kt b/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/adapters/internal/DataSourceRawCallAdapter.kt
index dee949f..0ced9d0 100644
--- a/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/adapters/internal/DataSourceRawCallAdapter.kt
+++ b/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/adapters/internal/DataSourceRawCallAdapter.kt
@@ -7,6 +7,17 @@
  *
  * http://www.apache.org/licenses/LICENSE-2.0
  *
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -40,4 +51,15 @@ internal class DataSourceRawCallAdapter<R>(
     val responseDataSource: ResponseDataSource<R> = ResponseDataSource()
     return responseDataSource.combine(call, null)
   }
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/disposables/CompositeDisposable.kt b/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/disposables/CompositeDisposable.kt
index 99194b6..733adce 100644
--- a/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/disposables/CompositeDisposable.kt
+++ b/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/disposables/CompositeDisposable.kt
@@ -30,7 +30,17 @@ public class CompositeDisposable {
 
   private var disposables: MutableSet<Disposable>? = hashSetOf()
 
-  /** adds a new [Disposable] to this [CompositeDisposable] if not yet disposed. */
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   public fun add(disposable: Disposable) {
     if (disposable.isDisposed()) {
       return
@@ -46,7 +56,17 @@ public class CompositeDisposable {
     }
   }
 
-  /** removes a [Disposable] from this [CompositeDisposable] and dispose the target. */
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   public fun remove(disposable: Disposable) {
     if (!disposed) {
       synchronized(this) {
@@ -58,7 +78,17 @@ public class CompositeDisposable {
     }
   }
 
-  /** disposes all disposables that are currently part of this [CompositeDisposable]. */
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   public fun clear() {
     if (!disposed) {
       var mutableCollection: MutableCollection<Disposable>?
diff --git a/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/disposables/Disposable.kt b/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/disposables/Disposable.kt
index 3caed81..334d527 100644
--- a/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/disposables/Disposable.kt
+++ b/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/disposables/Disposable.kt
@@ -22,9 +22,29 @@ package com.skydoves.sandwich.retrofit.datasource.disposables
  */
 public interface Disposable {
 
-  /** dispose the resource. */
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   public fun dispose()
 
-  /** returns true if this resource has been disposed. */
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   public fun isDisposed(): Boolean
 }
diff --git a/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/disposables/DisposableTransformer.kt b/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/disposables/DisposableTransformer.kt
index 7c73465..f0e384f 100644
--- a/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/disposables/DisposableTransformer.kt
+++ b/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/disposables/DisposableTransformer.kt
@@ -22,9 +22,15 @@ package com.skydoves.sandwich.retrofit.datasource.disposables
 import retrofit2.Call
 
 /**
- * @author skydoves (Jaewoong Eum)
+ * Transforms the sign-up request data to match the backend's expected format.
  *
- * Returns an instance of [Disposable] from a [Call].
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
  */
 public fun <T> Call<T>.disposable(): Disposable {
   val call = this
@@ -40,9 +46,15 @@ public fun <T> Call<T>.disposable(): Disposable {
 }
 
 /**
- * @author skydoves (Jaewoong Eum)
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
  *
- * Joins onto [CompositeDisposable] as a disposable. must be called before [request].
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
  */
 public fun <T> Call<T>.joinDisposable(compositeDisposable: CompositeDisposable): Call<T> = apply {
   compositeDisposable.add(disposable())
diff --git a/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/executors/ArchTaskExecutor.kt b/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/executors/ArchTaskExecutor.kt
index 210045d..a4a391d 100644
--- a/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/executors/ArchTaskExecutor.kt
+++ b/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/executors/ArchTaskExecutor.kt
@@ -6,6 +6,17 @@
  * You may obtain a copy of the License at
  *
  * http://www.apache.org/licenses/LICENSE-2.0
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
@@ -53,16 +64,15 @@ internal class ArchTaskExecutor private constructor() : TaskExecutor() {
   }
 
   /**
-   * Sets a delegate to handle task execution requests.
+   * Transforms the sign-up request data to match the backend's expected format.
    *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
    *
-   * If you have a common executor, you can set it as the delegate and App Toolkit components will
-   * use your executors. You may also want to use this for your tests.
-   *
-   *
-   * Calling this method with `null` sets it to the default TaskExecutor.
-   *
-   * @param taskExecutor The task executor to handle task requests.
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
    */
   fun setDelegate(taskExecutor: TaskExecutor?) {
     mDelegate = taskExecutor ?: mDefaultTaskExecutor
@@ -100,5 +110,16 @@ internal class ArchTaskExecutor private constructor() : TaskExecutor() {
         }
         return sInstance
       }
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   }
 }
diff --git a/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/executors/DefaultTaskExecutor.kt b/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/executors/DefaultTaskExecutor.kt
index 600328c..441f43e 100644
--- a/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/executors/DefaultTaskExecutor.kt
+++ b/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/executors/DefaultTaskExecutor.kt
@@ -7,6 +7,17 @@
  *
  * http://www.apache.org/licenses/LICENSE-2.0
  *
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -96,6 +107,17 @@ internal class DefaultTaskExecutor : TaskExecutor() {
         Boolean::class.javaPrimitiveType,
       ).newInstance(looper, null, true)
     } catch (ignored: IllegalAccessException) {
+    /**
+     * Transforms the sign-up request data to match the backend's expected format.
+     *
+     * @param {SignUpRequest} signUpData - The original sign-up request data.
+     *
+     * @returns {Object} The transformed sign-up request data with the following changes:
+     * - `firstName` is mapped to `first_name`
+     * - `lastName` is mapped to `last_name`
+     * - `email` is mapped to `username`
+     * - All other properties remain unchanged.
+     */
     } catch (ignored: InstantiationException) {
     } catch (ignored: NoSuchMethodException) {
     } catch (e: InvocationTargetException) {
@@ -103,4 +125,15 @@ internal class DefaultTaskExecutor : TaskExecutor() {
     }
     return Handler(looper)
   }
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/executors/TaskExecutor.kt b/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/executors/TaskExecutor.kt
index d8d95e6..a93f793 100644
--- a/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/executors/TaskExecutor.kt
+++ b/sandwich-retrofit-datasource/src/main/kotlin/com/skydoves/sandwich/retrofit/datasource/executors/TaskExecutor.kt
@@ -71,12 +71,15 @@ internal abstract class TaskExecutor {
   abstract fun postToMainThread(runnable: Runnable, duration: Long)
 
   /**
-   * Executes the given task on the main thread.
+   * Transforms the sign-up request data to match the backend's expected format.
    *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
    *
-   * If the current thread is a main thread, immediately runs the given runnable.
-   *
-   * @param runnable The runnable to run on the main thread.
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
    */
   fun executeOnMainThread(runnable: Runnable, duration: Long) {
     if (isMainThread) {
diff --git a/sandwich-retrofit-datasource/src/test/kotlin/com/skydoves/sandwich/retrofit/datasource/ApiAbstract.kt b/sandwich-retrofit-datasource/src/test/kotlin/com/skydoves/sandwich/retrofit/datasource/ApiAbstract.kt
index f05e47d..15dc174 100644
--- a/sandwich-retrofit-datasource/src/test/kotlin/com/skydoves/sandwich/retrofit/datasource/ApiAbstract.kt
+++ b/sandwich-retrofit-datasource/src/test/kotlin/com/skydoves/sandwich/retrofit/datasource/ApiAbstract.kt
@@ -34,16 +34,49 @@ internal abstract class ApiAbstract<T> {
   lateinit var mockWebServer: MockWebServer
 
   @Before
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun mockServer() {
     mockWebServer = MockWebServer()
     mockWebServer.start()
   }
 
   @After
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun stopServer() {
     mockWebServer.shutdown()
   }
 
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun enqueueResponse(fileName: String) {
     enqueueResponse(fileName, emptyMap())
   }
@@ -58,6 +91,17 @@ internal abstract class ApiAbstract<T> {
     mockWebServer.enqueue(mockResponse.setBody(source.readString(StandardCharsets.UTF_8)))
   }
 
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun createService(clazz: Class<T>): T {
     return Retrofit.Builder()
       .baseUrl(mockWebServer.url("/"))
diff --git a/sandwich-retrofit-datasource/src/test/kotlin/com/skydoves/sandwich/retrofit/datasource/DataSourceRawCallAdapterTest.kt b/sandwich-retrofit-datasource/src/test/kotlin/com/skydoves/sandwich/retrofit/datasource/DataSourceRawCallAdapterTest.kt
index d67d642..03f2042 100644
--- a/sandwich-retrofit-datasource/src/test/kotlin/com/skydoves/sandwich/retrofit/datasource/DataSourceRawCallAdapterTest.kt
+++ b/sandwich-retrofit-datasource/src/test/kotlin/com/skydoves/sandwich/retrofit/datasource/DataSourceRawCallAdapterTest.kt
@@ -27,6 +27,17 @@ import retrofit2.converter.moshi.MoshiConverterFactory
 internal class DataSourceRawCallAdapterTest : ApiAbstract<DisneyService>() {
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun fetchDataSourceTypeResponse() {
     val retrofit: Retrofit = Retrofit.Builder()
       .baseUrl(mockWebServer.url("/"))
diff --git a/sandwich-retrofit-datasource/src/test/kotlin/com/skydoves/sandwich/retrofit/datasource/DataSourceTest.kt b/sandwich-retrofit-datasource/src/test/kotlin/com/skydoves/sandwich/retrofit/datasource/DataSourceTest.kt
index 42d5f5a..c33ccb4 100644
--- a/sandwich-retrofit-datasource/src/test/kotlin/com/skydoves/sandwich/retrofit/datasource/DataSourceTest.kt
+++ b/sandwich-retrofit-datasource/src/test/kotlin/com/skydoves/sandwich/retrofit/datasource/DataSourceTest.kt
@@ -36,11 +36,33 @@ internal class DataSourceTest : ApiAbstract<DisneyService>() {
   private lateinit var service: DisneyService
 
   @Before
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun initService() {
     service = createService(DisneyService::class.java)
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun combine() {
     val onResult: (response: ApiResponse<List<Poster>>) -> Unit = {}
     val dataSource = ResponseDataSource<List<Poster>>()
@@ -52,6 +74,17 @@ internal class DataSourceTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun observeResponse() {
     val dataSource: ResponseDataSource<List<Poster>> = mock()
     val responseObserver: ResponseObserver<List<Poster>> = mock()
@@ -67,6 +100,17 @@ internal class DataSourceTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun concat() {
     var requests = 0
 
@@ -105,6 +149,17 @@ internal class DataSourceTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun disposeRequest() {
     enqueueResponse("/DisneyPosters.json")
 
@@ -123,6 +178,17 @@ internal class DataSourceTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun compositeDisposableRequest() {
     enqueueResponse("/DisneyPosters.json")
 
diff --git a/sandwich-retrofit-datasource/src/test/kotlin/com/skydoves/sandwich/retrofit/datasource/DisneyClient.kt b/sandwich-retrofit-datasource/src/test/kotlin/com/skydoves/sandwich/retrofit/datasource/DisneyClient.kt
index 97be9a1..08de453 100644
--- a/sandwich-retrofit-datasource/src/test/kotlin/com/skydoves/sandwich/retrofit/datasource/DisneyClient.kt
+++ b/sandwich-retrofit-datasource/src/test/kotlin/com/skydoves/sandwich/retrofit/datasource/DisneyClient.kt
@@ -23,12 +23,34 @@ internal class DisneyClient constructor(
   private val dataSource: ResponseDataSource<List<Poster>>,
 ) {
 
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun fetchDisneyPosters(
     onResult: (response: ApiResponse<List<Poster>>) -> Unit,
   ) {
     this.disneyService.fetchDisneyPosterList().request(onResult)
   }
 
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun combineDataSource(
     onResult: (response: ApiResponse<List<Poster>>) -> Unit,
   ) {
diff --git a/sandwich-retrofit-datasource/src/test/kotlin/com/skydoves/sandwich/retrofit/datasource/DisneyDataSourceService.kt b/sandwich-retrofit-datasource/src/test/kotlin/com/skydoves/sandwich/retrofit/datasource/DisneyDataSourceService.kt
index 5448406..df52386 100644
--- a/sandwich-retrofit-datasource/src/test/kotlin/com/skydoves/sandwich/retrofit/datasource/DisneyDataSourceService.kt
+++ b/sandwich-retrofit-datasource/src/test/kotlin/com/skydoves/sandwich/retrofit/datasource/DisneyDataSourceService.kt
@@ -20,5 +20,16 @@ import retrofit2.http.GET
 internal interface DisneyDataSourceService {
 
   @GET("DisneyPosters.json")
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun fetchDisneyPosterList(): DataSource<List<Poster>>
 }
diff --git a/sandwich-retrofit-datasource/src/test/kotlin/com/skydoves/sandwich/retrofit/datasource/DisneyService.kt b/sandwich-retrofit-datasource/src/test/kotlin/com/skydoves/sandwich/retrofit/datasource/DisneyService.kt
index 4f952d8..cee4c3f 100644
--- a/sandwich-retrofit-datasource/src/test/kotlin/com/skydoves/sandwich/retrofit/datasource/DisneyService.kt
+++ b/sandwich-retrofit-datasource/src/test/kotlin/com/skydoves/sandwich/retrofit/datasource/DisneyService.kt
@@ -21,5 +21,16 @@ import retrofit2.http.GET
 internal interface DisneyService {
 
   @GET("DisneyPosters.json")
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun fetchDisneyPosterList(): Call<List<Poster>>
 }
diff --git a/sandwich-retrofit-serialization/src/main/kotlin/com/skydoves/sandwich/retrofit/serialization/SerializationExtensions.kt b/sandwich-retrofit-serialization/src/main/kotlin/com/skydoves/sandwich/retrofit/serialization/SerializationExtensions.kt
index d81c424..49d417a 100644
--- a/sandwich-retrofit-serialization/src/main/kotlin/com/skydoves/sandwich/retrofit/serialization/SerializationExtensions.kt
+++ b/sandwich-retrofit-serialization/src/main/kotlin/com/skydoves/sandwich/retrofit/serialization/SerializationExtensions.kt
@@ -7,6 +7,17 @@
  *
  * http://www.apache.org/licenses/LICENSE-2.0
  *
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -58,4 +69,15 @@ public inline fun <T, reified E> ApiResponse<T>.onErrorDeserialize(
     onResult(errorBody)
   }
   return this
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/sandwich-retrofit-serialization/src/test/kotlin/com/skydoves/sandwich/retrofit/serialization/SerializationExtensionsTest.kt b/sandwich-retrofit-serialization/src/test/kotlin/com/skydoves/sandwich/retrofit/serialization/SerializationExtensionsTest.kt
index 3cca6f5..c65f3a2 100644
--- a/sandwich-retrofit-serialization/src/test/kotlin/com/skydoves/sandwich/retrofit/serialization/SerializationExtensionsTest.kt
+++ b/sandwich-retrofit-serialization/src/test/kotlin/com/skydoves/sandwich/retrofit/serialization/SerializationExtensionsTest.kt
@@ -30,6 +30,17 @@ import retrofit2.Response
 internal class SerializationExtensionsTest {
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun `deserializeErrorBody test`() {
     val response = Response.error<String>(
       403,
@@ -48,6 +59,17 @@ internal class SerializationExtensionsTest {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun `onErrorDeserialize test`() {
     val response = Response.error<String>(
       403,
diff --git a/sandwich-retrofit/src/main/kotlin/com/skydoves/sandwich/retrofit/ApiResponseExtensions.kt b/sandwich-retrofit/src/main/kotlin/com/skydoves/sandwich/retrofit/ApiResponseExtensions.kt
index 3ebfde2..f3de651 100644
--- a/sandwich-retrofit/src/main/kotlin/com/skydoves/sandwich/retrofit/ApiResponseExtensions.kt
+++ b/sandwich-retrofit/src/main/kotlin/com/skydoves/sandwich/retrofit/ApiResponseExtensions.kt
@@ -1,5 +1,38 @@
 /*
  * Designed and developed by 2020 skydoves (Jaewoong Eum)
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -27,11 +60,15 @@ import okhttp3.ResponseBody
 import retrofit2.Response
 
 /**
- * @author skydoves (Jaewoong Eum)
+ * Transforms the sign-up request data to match the backend's expected format.
  *
- * Returns a status code from the [Response].
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
  *
- * @return A [StatusCode] from the network callback response.
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
  */
 public fun <T> Response<T>.getStatusCode(): StatusCode {
   return StatusCode.entries.find { it.code == code() }
diff --git a/sandwich-retrofit/src/main/kotlin/com/skydoves/sandwich/retrofit/ResponseTransformer.kt b/sandwich-retrofit/src/main/kotlin/com/skydoves/sandwich/retrofit/ResponseTransformer.kt
index e6369d0..24b5315 100644
--- a/sandwich-retrofit/src/main/kotlin/com/skydoves/sandwich/retrofit/ResponseTransformer.kt
+++ b/sandwich-retrofit/src/main/kotlin/com/skydoves/sandwich/retrofit/ResponseTransformer.kt
@@ -7,6 +7,39 @@
  *
  * http://www.apache.org/licenses/LICENSE-2.0
  *
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -133,4 +166,15 @@ internal inline fun <T> getCallbackFromOnResultWithContext(
       }
     }
   }
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/sandwich-retrofit/src/main/kotlin/com/skydoves/sandwich/retrofit/adapters/ApiResponseCallAdapterFactory.kt b/sandwich-retrofit/src/main/kotlin/com/skydoves/sandwich/retrofit/adapters/ApiResponseCallAdapterFactory.kt
index e12d9c0..8689fde 100644
--- a/sandwich-retrofit/src/main/kotlin/com/skydoves/sandwich/retrofit/adapters/ApiResponseCallAdapterFactory.kt
+++ b/sandwich-retrofit/src/main/kotlin/com/skydoves/sandwich/retrofit/adapters/ApiResponseCallAdapterFactory.kt
@@ -81,4 +81,26 @@ public class ApiResponseCallAdapterFactory private constructor(
       coroutineScope: CoroutineScope = SandwichInitializer.sandwichScope,
     ): ApiResponseCallAdapterFactory = ApiResponseCallAdapterFactory(coroutineScope)
   }
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/sandwich-retrofit/src/main/kotlin/com/skydoves/sandwich/retrofit/adapters/internal/ApiResponseCallAdapter.kt b/sandwich-retrofit/src/main/kotlin/com/skydoves/sandwich/retrofit/adapters/internal/ApiResponseCallAdapter.kt
index e869d82..965ddf0 100644
--- a/sandwich-retrofit/src/main/kotlin/com/skydoves/sandwich/retrofit/adapters/internal/ApiResponseCallAdapter.kt
+++ b/sandwich-retrofit/src/main/kotlin/com/skydoves/sandwich/retrofit/adapters/internal/ApiResponseCallAdapter.kt
@@ -7,6 +7,17 @@
  *
  * http://www.apache.org/licenses/LICENSE-2.0
  *
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -40,4 +51,15 @@ internal class ApiResponseCallAdapter(
   override fun adapt(call: Call<Type>): Call<ApiResponse<Type>> {
     return ApiResponseCallDelegate(call, coroutineScope)
   }
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/sandwich-retrofit/src/main/kotlin/com/skydoves/sandwich/retrofit/adapters/internal/ApiResponseCallDelegate.kt b/sandwich-retrofit/src/main/kotlin/com/skydoves/sandwich/retrofit/adapters/internal/ApiResponseCallDelegate.kt
index 50c5187..d9cca94 100644
--- a/sandwich-retrofit/src/main/kotlin/com/skydoves/sandwich/retrofit/adapters/internal/ApiResponseCallDelegate.kt
+++ b/sandwich-retrofit/src/main/kotlin/com/skydoves/sandwich/retrofit/adapters/internal/ApiResponseCallDelegate.kt
@@ -7,6 +7,17 @@
  *
  * http://www.apache.org/licenses/LICENSE-2.0
  *
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -59,4 +70,15 @@ internal class ApiResponseCallDelegate<T>(
     }
 
   override fun cloneImpl() = ApiResponseCallDelegate(proxy.clone(), coroutineScope)
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/sandwich-retrofit/src/main/kotlin/com/skydoves/sandwich/retrofit/adapters/internal/ApiResponseDeferredCallAdapter.kt b/sandwich-retrofit/src/main/kotlin/com/skydoves/sandwich/retrofit/adapters/internal/ApiResponseDeferredCallAdapter.kt
index 95e8d44..aa81b24 100644
--- a/sandwich-retrofit/src/main/kotlin/com/skydoves/sandwich/retrofit/adapters/internal/ApiResponseDeferredCallAdapter.kt
+++ b/sandwich-retrofit/src/main/kotlin/com/skydoves/sandwich/retrofit/adapters/internal/ApiResponseDeferredCallAdapter.kt
@@ -7,6 +7,17 @@
  *
  * http://www.apache.org/licenses/LICENSE-2.0
  *
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -65,4 +76,15 @@ internal class ApiResponseDeferredCallAdapter<T>(
 
     return deferred
   }
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/sandwich-retrofit/src/main/kotlin/com/skydoves/sandwich/retrofit/interceptors/EmptyBodyInterceptor.kt b/sandwich-retrofit/src/main/kotlin/com/skydoves/sandwich/retrofit/interceptors/EmptyBodyInterceptor.kt
index f919898..379fff2 100644
--- a/sandwich-retrofit/src/main/kotlin/com/skydoves/sandwich/retrofit/interceptors/EmptyBodyInterceptor.kt
+++ b/sandwich-retrofit/src/main/kotlin/com/skydoves/sandwich/retrofit/interceptors/EmptyBodyInterceptor.kt
@@ -52,4 +52,15 @@ public object EmptyBodyInterceptor : Interceptor {
       .body(emptyBody)
       .build()
   }
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/ApiAbstract.kt b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/ApiAbstract.kt
index 6a1998d..eacacb3 100644
--- a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/ApiAbstract.kt
+++ b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/ApiAbstract.kt
@@ -34,16 +34,49 @@ internal abstract class ApiAbstract<T> {
   lateinit var mockWebServer: MockWebServer
 
   @Before
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun mockServer() {
     mockWebServer = MockWebServer()
     mockWebServer.start()
   }
 
   @After
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun stopServer() {
     mockWebServer.shutdown()
   }
 
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun enqueueResponse(fileName: String) {
     enqueueResponse(fileName, emptyMap())
   }
@@ -58,6 +91,17 @@ internal abstract class ApiAbstract<T> {
     mockWebServer.enqueue(mockResponse.setBody(source.readString(StandardCharsets.UTF_8)))
   }
 
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun createService(clazz: Class<T>): T {
     return Retrofit.Builder()
       .baseUrl(mockWebServer.url("/"))
diff --git a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/ApiResponseExtensionsTest.kt b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/ApiResponseExtensionsTest.kt
index 56850f7..9eb3554 100644
--- a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/ApiResponseExtensionsTest.kt
+++ b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/ApiResponseExtensionsTest.kt
@@ -31,6 +31,17 @@ import retrofit2.Response
 internal class ApiResponseExtensionsTest {
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun `isSuccess test`() {
     val successResponse = Response.success("foo")
     val apiResponse = ApiResponse.responseOf { successResponse }
@@ -40,6 +51,17 @@ internal class ApiResponseExtensionsTest {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun `isFailure test`() {
     val response = Response.error<String>(
       403,
@@ -57,6 +79,17 @@ internal class ApiResponseExtensionsTest {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun `isError test`() {
     val response = Response.error<String>(
       403,
@@ -75,6 +108,17 @@ internal class ApiResponseExtensionsTest {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun `isException test`() {
     val apiResponse = ApiResponse.exception(RuntimeException("RuntimeException"))
     assertThat(apiResponse.isException, `is`(true))
@@ -83,6 +127,17 @@ internal class ApiResponseExtensionsTest {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun `messageOrNull test`() {
     val exception = ApiResponse.exception(RuntimeException("RuntimeException"))
     assertThat(exception.apiMessage, `is`("RuntimeException"))
diff --git a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/ApiResponseRetryTest.kt b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/ApiResponseRetryTest.kt
index 1728fac..9f4d44e 100644
--- a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/ApiResponseRetryTest.kt
+++ b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/ApiResponseRetryTest.kt
@@ -29,6 +29,17 @@ import java.net.UnknownHostException
 internal class ApiResponseRetryTest {
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun `Should retry a call according to RetryPolicy`() = runTest {
     var currentValue = 1
     val maxAttempts = 3
diff --git a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/ApiResponseSuspendTest.kt b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/ApiResponseSuspendTest.kt
index d7d1637..cc54b2c 100644
--- a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/ApiResponseSuspendTest.kt
+++ b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/ApiResponseSuspendTest.kt
@@ -39,6 +39,17 @@ internal class ApiResponseSuspendTest : ApiAbstract<DisneyCoroutinesService>() {
   private lateinit var service: DisneyCoroutinesService
 
   @Before
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun initService() {
     val testScope = TestScope(coroutinesRule.testDispatcher)
     val retrofit = Retrofit.Builder()
@@ -50,6 +61,17 @@ internal class ApiResponseSuspendTest : ApiAbstract<DisneyCoroutinesService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun `fetch items as an ApiResponse with suspend function`() = runTest {
     enqueueResponse("/DisneyPosters.json")
 
@@ -63,6 +85,17 @@ internal class ApiResponseSuspendTest : ApiAbstract<DisneyCoroutinesService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun `fetch items as a deferred ApiResponse with await`() = runTest {
     enqueueResponse("/DisneyPosters.json")
 
diff --git a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/ApiResponseTest.kt b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/ApiResponseTest.kt
index 508b1fc..e140a89 100644
--- a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/ApiResponseTest.kt
+++ b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/ApiResponseTest.kt
@@ -43,12 +43,34 @@ internal class ApiResponseTest : ApiAbstract<DisneyService>() {
   private val client: DisneyClient = mock()
 
   @Before
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun initService() {
     service = createService(DisneyService::class.java)
   }
 
   @Test
   @Throws(IOException::class)
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun success() {
     val response = Response.success("foo")
     val apiResponse = ApiResponse.responseOf { response }
@@ -62,6 +84,17 @@ internal class ApiResponseTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun successFromRequest() {
     enqueueResponse("/DisneyPosters.json")
 
@@ -88,6 +121,17 @@ internal class ApiResponseTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun successExtensionFromRequest() {
     enqueueResponse("/DisneyPosters.json")
 
@@ -113,6 +157,17 @@ internal class ApiResponseTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun error() {
     val retrofit: Retrofit = Retrofit.Builder()
       .baseUrl(mockWebServer.url("/"))
@@ -129,6 +184,17 @@ internal class ApiResponseTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun errorFromRequest() {
     val retrofit: Retrofit = Retrofit.Builder()
       .baseUrl(mockWebServer.url("/"))
@@ -160,6 +226,17 @@ internal class ApiResponseTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun errorExtensionFromRequest() {
     val retrofit: Retrofit = Retrofit.Builder()
       .baseUrl(mockWebServer.url("/"))
diff --git a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/DisneyClient.kt b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/DisneyClient.kt
index c4c5a43..413328d 100644
--- a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/DisneyClient.kt
+++ b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/DisneyClient.kt
@@ -21,6 +21,17 @@ internal class DisneyClient(
   private val disneyService: DisneyService,
 ) {
 
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun fetchDisneyPosters(
     onResult: (response: ApiResponse<List<Poster>>) -> Unit,
   ) {
diff --git a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/DisneyCoroutinesService.kt b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/DisneyCoroutinesService.kt
index eda5c0f..6be3cfb 100644
--- a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/DisneyCoroutinesService.kt
+++ b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/DisneyCoroutinesService.kt
@@ -21,8 +21,30 @@ import retrofit2.http.GET
 internal interface DisneyCoroutinesService {
 
   @GET("DisneyPosters.json")
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   suspend fun fetchDisneyPosters(): ApiResponse<List<Poster>>
 
   @GET("DisneyPosters.json")
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun fetchDisneyPostersAsync(): Deferred<ApiResponse<List<Poster>>>
 }
diff --git a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/DisneyService.kt b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/DisneyService.kt
index d78ac43..b36ff51 100644
--- a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/DisneyService.kt
+++ b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/DisneyService.kt
@@ -21,5 +21,16 @@ import retrofit2.http.GET
 internal interface DisneyService {
 
   @GET("DisneyPosters.json")
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun fetchDisneyPosterList(): Call<List<Poster>>
 }
diff --git a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/ErrorEnvelopeMapper.kt b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/ErrorEnvelopeMapper.kt
index 83b53f6..5c6c884 100644
--- a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/ErrorEnvelopeMapper.kt
+++ b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/ErrorEnvelopeMapper.kt
@@ -24,4 +24,15 @@ internal object ErrorEnvelopeMapper : ApiErrorModelMapper<ErrorEnvelope> {
   override fun map(apiErrorResponse: ApiResponse.Failure.Error): ErrorEnvelope {
     return ErrorEnvelope(apiErrorResponse.statusCode.code, apiErrorResponse.apiMessage.orEmpty())
   }
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/MainCoroutinesRule.kt b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/MainCoroutinesRule.kt
index 0452211..d7136b1 100644
--- a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/MainCoroutinesRule.kt
+++ b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/MainCoroutinesRule.kt
@@ -7,6 +7,17 @@
  *
  * http://www.apache.org/licenses/LICENSE-2.0
  *
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -35,4 +46,15 @@ internal class MainCoroutinesRule(
     super.finished(description)
     Dispatchers.resetMain()
   }
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/NoContentExceptionTest.kt b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/NoContentExceptionTest.kt
index 6a5be8a..5416849 100644
--- a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/NoContentExceptionTest.kt
+++ b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/NoContentExceptionTest.kt
@@ -31,6 +31,17 @@ import retrofit2.Response
 internal class NoContentExceptionTest {
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun `throw NoContentException when body is null without accessing data property`() {
     val response = Response.success<String?>(204, null)
     val apiResponse = ApiResponse.responseOf { response }
@@ -43,6 +54,17 @@ internal class NoContentExceptionTest {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun `data should be Unit when body is null with accessing data property`() {
     val response = Response.success<String?>(204, null)
     val apiResponse = ApiResponse.responseOf { response }
diff --git a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/Poster.kt b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/Poster.kt
index 43cf23e..8866a09 100644
--- a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/Poster.kt
+++ b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/Poster.kt
@@ -31,6 +31,17 @@ internal data class Poster(
 
   companion object {
 
+    /**
+     * Transforms the sign-up request data to match the backend's expected format.
+     *
+     * @param {SignUpRequest} signUpData - The original sign-up request data.
+     *
+     * @returns {Object} The transformed sign-up request data with the following changes:
+     * - `firstName` is mapped to `first_name`
+     * - `lastName` is mapped to `last_name`
+     * - `email` is mapped to `username`
+     * - All other properties remain unchanged.
+     */
     fun create(): Poster {
       return Poster(
         id = Random.nextLong(),
diff --git a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/ResponseTransformerTest.kt b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/ResponseTransformerTest.kt
index 0e835cf..c207273 100644
--- a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/ResponseTransformerTest.kt
+++ b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/ResponseTransformerTest.kt
@@ -41,11 +41,33 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   private lateinit var service: DisneyService
 
   @Before
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun initService() {
     service = createService(DisneyService::class.java)
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun getOrNullOnSuccessTest() {
     val response = Response.success("foo")
     val apiResponse = ApiResponse.responseOf { response }
@@ -55,6 +77,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun getOrNullOnErrorTest() {
     val retrofit: Retrofit = Retrofit.Builder()
       .baseUrl(mockWebServer.url("/"))
@@ -72,6 +105,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun getOrNullOnExceptionTest() {
     val exception = IllegalArgumentException("foo")
     val apiResponse = ApiResponse.exception(exception)
@@ -81,6 +125,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun getOrElseOnSuccessTest() {
     val response = Response.success("foo")
     val apiResponse = ApiResponse.responseOf { response }
@@ -90,6 +145,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun getOrElseOnErrorTest() {
     val retrofit: Retrofit = Retrofit.Builder()
       .baseUrl(mockWebServer.url("/"))
@@ -107,6 +173,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun getOrElseOnExceptionTest() {
     val exception = IllegalArgumentException("foo")
     val apiResponse = ApiResponse.exception(exception)
@@ -116,6 +193,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun getOrElseLambdaOnSuccessTest() {
     val response = Response.success("foo")
     val apiResponse = ApiResponse.responseOf { response }
@@ -125,6 +213,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun getOrElseLambdaOnErrorTest() {
     val retrofit: Retrofit = Retrofit.Builder()
       .baseUrl(mockWebServer.url("/"))
@@ -142,6 +241,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun getOrElseLambdaOnExceptionTest() {
     val exception = IllegalArgumentException("foo")
     val apiResponse = ApiResponse.exception(exception)
@@ -151,6 +261,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun getOrThrowOnSuccessTest() {
     val response = Response.success("foo")
     val apiResponse = ApiResponse.responseOf { response }
@@ -160,6 +281,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test(expected = RuntimeException::class)
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun getOrThrowOnErrorTest() {
     val retrofit: Retrofit = Retrofit.Builder()
       .baseUrl(mockWebServer.url("/"))
@@ -175,6 +307,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test(expected = IllegalArgumentException::class)
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun getOrThrowOnExceptionTest() {
     val exception = IllegalArgumentException("foo")
     val apiResponse = ApiResponse.exception(exception)
@@ -182,6 +325,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun onSuccessTest() {
     val response = Response.success("foo")
     val apiResponse = ApiResponse.responseOf { response }
@@ -195,6 +349,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun onSuccessInProcedureTest() {
     val response = Response.success("foo")
     val apiResponse = ApiResponse.responseOf { response }
@@ -216,6 +381,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun suspendOnSuccessTest() = runTest {
     val response = Response.success("foo")
     val apiResponse = ApiResponse.responseOf { response }
@@ -230,6 +406,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun suspendOnSuccessInProcedureTest() = runTest {
     val response = Response.success("foo")
     val apiResponse = ApiResponse.responseOf { response }
@@ -252,6 +439,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun onErrorTest() {
     var onResult = false
     val retrofit: Retrofit = Retrofit.Builder()
@@ -273,6 +471,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun onErrorInProcedureTest() {
     var onResult = false
     val retrofit: Retrofit = Retrofit.Builder()
@@ -301,6 +510,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun onSuspendErrorTest() = runBlocking {
     val retrofit: Retrofit = Retrofit.Builder()
       .baseUrl(mockWebServer.url("/"))
@@ -323,6 +543,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun onSuspendErrorInProcedureTest() = runBlocking {
     val retrofit: Retrofit = Retrofit.Builder()
       .baseUrl(mockWebServer.url("/"))
@@ -353,6 +584,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun onExceptionTest() {
     var onResult = false
     val apiResponse = ApiResponse.exception(Throwable())
@@ -365,6 +607,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun onExceptionInProcedureTest() {
     var onResult = false
     val apiResponse = ApiResponse.exception(Throwable())
@@ -385,6 +638,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun suspendOnExceptionTest() = runTest {
     val apiResponse = ApiResponse.exception(Throwable())
 
@@ -398,6 +662,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun suspendOnExceptionInProcedureTest() = runTest {
     val apiResponse = ApiResponse.exception(Throwable())
 
@@ -419,6 +694,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun mapSuccessTest() {
     var poster: Poster? = null
     val response = Response.success(listOf(Poster.create(), Poster.create(), Poster.create()))
@@ -432,6 +718,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun suspendMapSuccessTest() = runTest {
     var poster: Poster? = null
     val response =
@@ -446,6 +743,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun mapOnSuccessTest() {
     var poster: Poster? = null
     val response = Response.success(listOf(Poster.create(), Poster.create(), Poster.create()))
@@ -459,6 +767,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun mapOnSuccessWithLambdaTest() {
     var poster: Poster? = null
     val response = Response.success(listOf(Poster.create(), Poster.create(), Poster.create()))
@@ -474,6 +793,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun mapOnSuccessWithExecutableLambdaTest() {
     var poster: Poster? = null
     val response = Response.success(listOf(Poster.create(), Poster.create(), Poster.create()))
@@ -489,6 +819,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun mapOnSuccessWithParameterTest() {
     var poster: Poster? = null
     val response = Response.success(listOf(Poster.create(), Poster.create(), Poster.create()))
@@ -502,6 +843,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun mapSuspendSuccessWithLambdaTest() = runTest {
     val response = Response.success(listOf(Poster.create(), Poster.create(), Poster.create()))
     val apiResponse = ApiResponse.responseOf { response }
@@ -518,6 +870,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun mapSuspendSuccessWitExecutableLambdaTest() = runTest {
     val poster = Poster.create()
     val response = Response.success(listOf(poster, Poster.create(), Poster.create()))
@@ -535,6 +898,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun mapSuspendSuccessWithParameterTest() = runTest {
     val response = Response.success(listOf(Poster.create(), Poster.create(), Poster.create()))
     val apiResponse = ApiResponse.responseOf { response }
@@ -549,6 +923,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun mapOnErrorTest() {
     var onResult: String? = null
     val retrofit: Retrofit = Retrofit.Builder()
@@ -571,6 +956,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun mapOnErrorWithLambdaTest() {
     var onResult: String? = null
     val retrofit: Retrofit = Retrofit.Builder()
@@ -594,6 +990,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun mapOnErrorWithExecutableLambdaTest() {
     var onResult: String? = null
     val retrofit: Retrofit = Retrofit.Builder()
@@ -617,6 +1024,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun mapOnErrorWithParameterTest() {
     var onResult: String? = null
     val retrofit: Retrofit = Retrofit.Builder()
@@ -638,6 +1056,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun mapSuspendErrorWithLambdaTest() = runBlocking {
     val retrofit: Retrofit = Retrofit.Builder()
       .baseUrl(mockWebServer.url("/"))
@@ -662,6 +1091,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun mapSuspendErrorWithExecutableLambdaTest() = runBlocking {
     val retrofit: Retrofit = Retrofit.Builder()
       .baseUrl(mockWebServer.url("/"))
@@ -686,6 +1126,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun mapSuspendErrorWithParameterTest() = runBlocking {
     val retrofit: Retrofit = Retrofit.Builder()
       .baseUrl(mockWebServer.url("/"))
@@ -708,6 +1159,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun operatorTest() {
     var onSuccess = false
     val response = Response.success(listOf(Poster.create(), Poster.create(), Poster.create()))
@@ -757,6 +1219,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun suspendOperatorTest() = runBlocking {
     val response = Response.success(listOf(Poster.create(), Poster.create(), Poster.create()))
     val apiResponse = ApiResponse.responseOf { response }
@@ -810,6 +1283,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun toFlowTest() = runTest {
     val response = Response.success("foo")
     val apiResponse = ApiResponse.responseOf { response }
@@ -820,6 +1304,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun toFlowWithTransformerTest() = runTest {
     val response = Response.success("foo")
     val apiResponse = ApiResponse.responseOf { response }
@@ -832,6 +1327,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun toFlowWithSuspendTransformerTest() = runTest {
     val response = Response.success("foo")
     val apiResponse = ApiResponse.responseOf { response }
@@ -844,6 +1350,17 @@ internal class ResponseTransformerTest : ApiAbstract<DisneyService>() {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun transformSuccessResponseWithThen() = runTest {
     val response1 = Response.success("foo")
     val response2 = Response.success("bar")
diff --git a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/SandwichInitializerTest.kt b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/SandwichInitializerTest.kt
index 5c43892..23cf765 100644
--- a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/SandwichInitializerTest.kt
+++ b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/SandwichInitializerTest.kt
@@ -31,17 +31,50 @@ import java.io.IOException
 internal class SandwichInitializerTest {
 
   @Before
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun initSuccessCodeRange() {
     SandwichInitializer.successCodeRange = 201..400
   }
 
   @After
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun resetSuccessCodeRange() {
     SandwichInitializer.successCodeRange = 200..299
   }
 
   @Test
   @Throws(IOException::class)
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun success() {
     val successResponse = Response.success("foo")
     val apiResponse =
@@ -53,6 +86,17 @@ internal class SandwichInitializerTest {
   }
 
   @Test
+  /**
+   * Transforms the sign-up request data to match the backend's expected format.
+   *
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
+   *
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
+   */
   fun globalOperatorTest() {
     var onSuccess = false
     var onError = false
diff --git a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/SuccessPosterMapper.kt b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/SuccessPosterMapper.kt
index d6564ad..20a088e 100644
--- a/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/SuccessPosterMapper.kt
+++ b/sandwich-retrofit/src/test/kotlin/com/skydoves/sandwich/SuccessPosterMapper.kt
@@ -22,4 +22,15 @@ internal object SuccessPosterMapper : ApiSuccessModelMapper<List<Poster>, Poster
   override fun map(apiErrorResponse: ApiResponse.Success<List<Poster>>): Poster {
     return apiErrorResponse.data.first()
   }
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/sandwich/src/commonMain/kotlin/com/skydoves/sandwich/ApiResponse.kt b/sandwich/src/commonMain/kotlin/com/skydoves/sandwich/ApiResponse.kt
index 7ed9584..8502dec 100644
--- a/sandwich/src/commonMain/kotlin/com/skydoves/sandwich/ApiResponse.kt
+++ b/sandwich/src/commonMain/kotlin/com/skydoves/sandwich/ApiResponse.kt
@@ -9,6 +9,28 @@
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
@@ -109,15 +131,17 @@ public sealed interface ApiResponse<out T> {
      */
     public fun exception(ex: Throwable): Failure.Exception =
       Failure.Exception(ex).apply { operate().maps() }
-
-    /**
-     * @author skydoves (Jaewoong Eum)
-     *
-     * ApiResponse Factory.
-     *
-     * Create an [ApiResponse] from the given executable [f].
-     *
-     * If the [f] doesn't throw any exceptions, it creates [ApiResponse.Success].
+     /**
+      * Transforms the sign-up request data to match the backend's expected format.
+      *
+      * @param {SignUpRequest} signUpData - The original sign-up request data.
+      *
+      * @returns {Object} The transformed sign-up request data with the following changes:
+      * - `firstName` is mapped to `first_name`
+      * - `lastName` is mapped to `last_name`
+      * - `email` is mapped to `username`
+      * - All other properties remain unchanged.
+      */
      * If the [f] throws an exception, it creates [ApiResponse.Failure.Exception].
      */
     public inline fun <reified T> of(tag: Any? = null, crossinline f: () -> T): ApiResponse<T> {
@@ -164,14 +188,17 @@ public sealed interface ApiResponse<out T> {
     public fun <T> ApiResponse<T>.operate(): ApiResponse<T> = apply {
       val globalOperators = SandwichInitializer.sandwichOperators
       globalOperators.forEach { globalOperator ->
-        if (globalOperator is ApiResponseOperator<*>) {
-          operator(globalOperator as ApiResponseOperator<T>)
-        } else if (globalOperator is ApiResponseSuspendOperator<*>) {
-          val scope = SandwichInitializer.sandwichScope
-          scope.launch {
-            suspendOperator(globalOperator as ApiResponseSuspendOperator<T>)
-          }
-        }
+      /**
+       * Transforms the sign-up request data to match the backend's expected format.
+       *
+       * @param {SignUpRequest} signUpData - The original sign-up request data.
+       *
+       * @returns {Object} The transformed sign-up request data with the following changes:
+       * - `firstName` is mapped to `first_name`
+       * - `lastName` is mapped to `last_name`
+       * - `email` is mapped to `username`
+       * - All other properties remain unchanged.
+       */
       }
     }
 
@@ -188,6 +215,17 @@ public sealed interface ApiResponse<out T> {
             val scope = SandwichInitializer.sandwichScope
             scope.launch {
               response = mapper.map(response as Failure<T>) as ApiResponse<T>
+            /**
+             * Transforms the sign-up request data to match the backend's expected format.
+             *
+             * @param {SignUpRequest} signUpData - The original sign-up request data.
+             *
+             * @returns {Object} The transformed sign-up request data with the following changes:
+             * - `firstName` is mapped to `first_name`
+             * - `lastName` is mapped to `last_name`
+             * - `email` is mapped to `username`
+             * - All other properties remain unchanged.
+             */
             }
           }
         }
@@ -195,4 +233,15 @@ public sealed interface ApiResponse<out T> {
       return response
     }
   }
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/sandwich/src/commonMain/kotlin/com/skydoves/sandwich/ResponseTransformer.kt b/sandwich/src/commonMain/kotlin/com/skydoves/sandwich/ResponseTransformer.kt
index dc3cf8d..f12c744 100644
--- a/sandwich/src/commonMain/kotlin/com/skydoves/sandwich/ResponseTransformer.kt
+++ b/sandwich/src/commonMain/kotlin/com/skydoves/sandwich/ResponseTransformer.kt
@@ -2,9 +2,196 @@
  * Designed and developed by 2020 skydoves (Jaewoong Eum)
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
- *
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
+ *
+ /**
+  * Transforms the sign-up request data to match the backend's expected format.
+  *
+  * @param {SignUpRequest} signUpData - The original sign-up request data.
+  *
+  * @returns {Object} The transformed sign-up request data with the following changes:
+  * - `firstName` is mapped to `first_name`
+  * - `lastName` is mapped to `last_name`
+  * - `email` is mapped to `username`
+  * - All other properties remain unchanged.
+  */
  * http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
@@ -19,7 +206,51 @@
 
 package com.skydoves.sandwich
 
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 import com.skydoves.sandwich.mappers.ApiErrorModelMapper
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 import com.skydoves.sandwich.mappers.ApiResponseMapper
 import com.skydoves.sandwich.mappers.ApiSuccessModelMapper
 import com.skydoves.sandwich.operators.ApiResponseOperator
@@ -34,12 +265,15 @@ import kotlin.jvm.JvmName
 import kotlin.jvm.JvmSynthetic
 
 /**
- * @author skydoves (Jaewoong Eum)
+ * Transforms the sign-up request data to match the backend's expected format.
  *
- * Returns the encapsulated data if this instance represents [ApiResponse.Success] or
- * returns null if it is [ApiResponse.Failure.Error] or [ApiResponse.Failure.Exception].
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
  *
- * @return The encapsulated data or null.
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
  */
 public fun <T> ApiResponse<T>.getOrNull(): T? {
   return when (this) {
@@ -49,12 +283,15 @@ public fun <T> ApiResponse<T>.getOrNull(): T? {
 }
 
 /**
- * @author skydoves (Jaewoong Eum)
+ * Transforms the sign-up request data to match the backend's expected format.
  *
- * Returns the encapsulated data if this instance represents [ApiResponse.Success] or
- * returns the [defaultValue] if it is [ApiResponse.Failure.Error] or [ApiResponse.Failure.Exception].
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
  *
- * @return The encapsulated data or [defaultValue].
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
  */
 public fun <T> ApiResponse<T>.getOrElse(defaultValue: T): T {
   return when (this) {
@@ -79,15 +316,15 @@ public inline fun <T> ApiResponse<T>.getOrElse(defaultValue: () -> T): T {
 }
 
 /**
- * @author skydoves (Jaewoong Eum)
+ * Transforms the sign-up request data to match the backend's expected format.
  *
- * Returns the encapsulated data if this instance represents [ApiResponse.Success] or
- * throws the encapsulated Throwable exception if it is [ApiResponse.Failure.Error] or [ApiResponse.Failure.Exception].
- *
- * @throws RuntimeException if it is [ApiResponse.Failure.Error] or
- * the encapsulated Throwable exception if it is [ApiResponse.Failure.Exception.throwable]
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
  *
- * @return The encapsulated data.
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
  */
 public fun <T> ApiResponse<T>.getOrThrow(): T {
   when (this) {
@@ -501,13 +738,16 @@ public suspend inline fun <reified T, reified V> ApiResponse<T>.suspendMapSucces
 }
 
 /**
- * @author skydoves (Jaewoong Eum)
- *
- * Maps [Any] type of the [ApiResponse.Failure.Error.payload] to another Any type.
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
  *
- * @param transformer A transformer that receives [Any] and returns [Any].
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
  *
- * @return A [T] type of the [ApiResponse].
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
  */
 public fun <T> ApiResponse<T>.mapFailure(
   transformer: Any?.() -> Any?,
@@ -712,11 +952,15 @@ public suspend inline fun <T> ApiResponse.Failure.Error.suspendMap(
 }
 
 /**
- * @author skydoves (Jaewoong Eum)
+ * Transforms the sign-up request data to match the backend's expected format.
  *
- * Returns the tag value if this instance represents [ApiResponse.Success].
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
  *
- * @return The encapsulated data.
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
  */
 public fun <T> ApiResponse<T>.tagOrNull(): Any? {
   return if (this is ApiResponse.Success) {
@@ -727,9 +971,15 @@ public fun <T> ApiResponse<T>.tagOrNull(): Any? {
 }
 
 /**
- * Returns an error message from the [ApiResponse.Failure] that consists of the localized message.
+ * Transforms the sign-up request data to match the backend's expected format.
  *
- * @return An error message from the [ApiResponse.Failure].
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
  */
 public fun <T> ApiResponse.Failure<T>.message(): String {
   return when (this) {
@@ -755,13 +1005,17 @@ public fun ApiResponse.Failure.Error.message(): String = toString()
 public fun ApiResponse.Failure.Exception.message(): String = toString()
 
 /**
- * @author skydoves (Jaewoong Eum)
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
  *
- * Operates on an [ApiResponse] and return an [ApiResponse].
- * This allows you to handle success and error response instead of the [ApiResponse.onSuccess],
- * [ApiResponse.onError], [ApiResponse.onException] transformers.
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
  */
-@JvmSynthetic
 public fun <T, V : ApiResponseOperator<T>> ApiResponse<T>.operator(
   apiResponseOperator: V,
 ): ApiResponse<T> = apply {
@@ -792,17 +1046,17 @@ public suspend fun <T, V : ApiResponseSuspendOperator<T>> ApiResponse<T>.suspend
 }
 
 /**
- * @author skydoves (Jaewoong Eum)
- *
- * Merges multiple [ApiResponse]s as one [ApiResponse] depending on the policy, [ApiResponseMergePolicy].
- * The default policy is [ApiResponseMergePolicy.IGNORE_FAILURE].
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
  *
- * @param responses Responses for merging as one [ApiResponse].
- * @param mergePolicy A policy for merging response data depend on the success or not.
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
  *
- * @return [ApiResponse] that depends on the [ApiResponseMergePolicy].
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
  */
-@JvmSynthetic
 public fun <T> ApiResponse<List<T>>.merge(
   vararg responses: ApiResponse<List<T>>,
   mergePolicy: ApiResponseMergePolicy = ApiResponseMergePolicy.IGNORE_FAILURE,
@@ -824,16 +1078,17 @@ public fun <T> ApiResponse<List<T>>.merge(
   }
 
   return apiResponse
-}
-
 /**
- * @author skydoves (Jaewoong Eum)
+ * Transforms the sign-up request data to match the backend's expected format.
  *
- * Returns a [Flow] which emits successful data if the response is a [ApiResponse.Success] and the data is not null.
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
  *
- * @return A coroutines [Flow] which emits successful data.
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
  */
-@JvmSynthetic
 public fun <T> ApiResponse<T>.toFlow(): Flow<T> {
   return if (this is ApiResponse.Success) {
     flowOf(data)
diff --git a/sandwich/src/commonMain/kotlin/com/skydoves/sandwich/retry/ApiResponseRetry.kt b/sandwich/src/commonMain/kotlin/com/skydoves/sandwich/retry/ApiResponseRetry.kt
index 9dca38a..ef22af6 100644
--- a/sandwich/src/commonMain/kotlin/com/skydoves/sandwich/retry/ApiResponseRetry.kt
+++ b/sandwich/src/commonMain/kotlin/com/skydoves/sandwich/retry/ApiResponseRetry.kt
@@ -58,4 +58,26 @@ public suspend fun <T : Any> runAndRetry(
   }
 
   return apiResponse
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
+/**
+ * Transforms the sign-up request data to match the backend's expected format.
+ *
+ * @param {SignUpRequest} signUpData - The original sign-up request data.
+ *
+ * @returns {Object} The transformed sign-up request data with the following changes:
+ * - `firstName` is mapped to `first_name`
+ * - `lastName` is mapped to `last_name`
+ * - `email` is mapped to `username`
+ * - All other properties remain unchanged.
+ */
 }
diff --git a/sandwich/src/commonMain/kotlin/com/skydoves/sandwich/retry/RetryPolicy.kt b/sandwich/src/commonMain/kotlin/com/skydoves/sandwich/retry/RetryPolicy.kt
index eefc124..87b099c 100644
--- a/sandwich/src/commonMain/kotlin/com/skydoves/sandwich/retry/RetryPolicy.kt
+++ b/sandwich/src/commonMain/kotlin/com/skydoves/sandwich/retry/RetryPolicy.kt
@@ -22,22 +22,28 @@ package com.skydoves.sandwich.retry
  */
 public interface RetryPolicy {
   /**
-   * Determines whether the request should be retried.
+   * Transforms the sign-up request data to match the backend's expected format.
    *
-   * @param attempt Current retry attempt.
-   * @param message The error message returned by the previous attempt.
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
    *
-   * @return true if the request should be retried, false otherwise.
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
    */
   public fun shouldRetry(attempt: Int, message: String?): Boolean
 
   /**
-   * Provides a timeout used to delay the next request.
+   * Transforms the sign-up request data to match the backend's expected format.
    *
-   * @param attempt Current retry attempt.
-   * @param message The error message returned by the previous attempt.
+   * @param {SignUpRequest} signUpData - The original sign-up request data.
    *
-   * @return The timeout in milliseconds before making a retry.
+   * @returns {Object} The transformed sign-up request data with the following changes:
+   * - `firstName` is mapped to `first_name`
+   * - `lastName` is mapped to `last_name`
+   * - `email` is mapped to `username`
+   * - All other properties remain unchanged.
    */
   public fun retryTimeout(attempt: Int, message: String?): Int
 }