docs: add integration tests documentation and tutorials

tests/integration-tests/CONTRIBUTING.md

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+# Contributing to integration tests
+
+Please, read this guide before contributing to integration tests.
+
+## Adding new scenario
+
+To add new scenario, follow these steps:
+1. Create a new feature file in the `src/test/resources/features/new_feature` folder.
+2. Implement steps definitions in the `src/test/kotlin/features/new_feature` folder.
+3. Test the scenario properly, make sure it works for different configurations.
+4. Submit a pull request with the new scenario.
+
+When creating a new scenario, please, follow the coding rules guidelines represented in the next section.
+
+## Coding rules
+
+### Always use constants for test data
+
+Do not use hardcoded values in the tests. Always use constants instead.
+Instead of adding `Name` and `Surname` to the test, add `NAME` and `SURNAME` constants to the `common.TestConstants` class.
+
+This approach has the following advantages:
+* It is easier to find and change the test data.
+* It is easier to understand the test logic.
+* It is easier to reuse the test data in other tests.
+
+### Naming conventions
+
+* `camelCase` is used for naming variables, methods, and classes.
+* `UPPER_SNAKE_CASE` is used for naming constants.
+* `snakecase` is used for naming files and folders.
+
+### Use Cucumber best practices
+
+Use [Cucumber best practices](https://www.browserstack.com/guide/cucumber-best-practices-for-testing) when writing Gherkin scenarios.
+
+### Waiting must always be asynchronous
+
+Do not use `Thread.sleep` to wait for the result of an asynchronous operation.
+Use [Awaitility](http://www.awaitility.org/) instead. The `wait` method is implemented in the `common.Utils` object.
+
+Wrong usage example:
+```kotlin
+for(i in 1..10) {
+    val didEvent =
+        ListenToEvents.`as`(actor).didEvents.lastOrNull {
+            it.data.did == actor.recall<String>("shortFormDid")
+        }
+    if (didEvent != null && didEvent.data.status == "PUBLISHED") {
+        break
+    }
+    Thread.sleep(5000)
+}
+```
+
+Correct usage example:
+```kotlin
+wait(
+    {
+        val didEvent =
+            ListenToEvents.`as`(actor).didEvents.lastOrNull {
+                it.data.did == actor.recall<String>("shortFormDid")
+            }
+        didEvent != null && didEvent.data.status == "PUBLISHED"
+    },
+    "ERROR: DID was not published to ledger!",
+    timeout = TestConstants.DID_UPDATE_PUBLISH_MAX_WAIT_5_MIN
+)
+```
+
+### Sharing context between steps
+
+Actor can use `remember` and `recall` methods to share context between steps.
+The `remember` method stores the value in the actor's memory,
+and the `recall` method retrieves the value from the actor's memory.
+
+Usage example:
+```kotlin
+// Remember connection in some step
+val connection = SerenityRest.lastResponse().get<Connection>()
+inviter.remember("connection", connection)
+//...
+// Recalls connection in some other step
+val connection = inviter.recall<Connection>("connection")
+```
+
+### Independent scenarios
+
+Scenarios must be independent of each other. Do not use the state from one scenario in another scenario.
+
+It allows you to run scenarios in parallel and avoid unexpected test failures.