Document check storage endpoint (#589)

docusaurus/video/docusaurus/docs/api/_common_/storage.mdx

@@ -14,7 +14,10 @@ If you need support for a different storage provider, you can participate in the
 To use your own storage you need to:
 
 1. Configure a new storage for your Stream application
-2. Configure your call type(s) to use the new storage
+2. (Optional) Check storage configuration for correctness.
+    Calling check endpoint will create a test markdown file in the storage to verify the configuration. It will return an error if the file is not created.
+    In case of success, the file with`stream-<uuid>.md` will be uploaded to the storage. Every time you call this endpoint, a new file will be created.
+3. Configure your call type(s) to use the new storage
 
 Once the setup is complete, call recordings and transcription files will be automatically stored in your own storage.
 
@@ -35,7 +38,13 @@ await serverSideClient.createExternalStorage({
     },
 });
 
-// 2. update the call type to use the new storage
+// 2. (Optional) Check storage configuration for correctness
+// In case of any errors, this will throw a ResponseError.
+await serverSideClient.checkExternalStorage({
+    name: 'my-s3'
+});
+
+// 3. update the call type to use the new storage
 await serverSideClient.updateCallType('my-call-type', {
     external_storage: "my-s3",
 });
@@ -44,10 +53,10 @@ await serverSideClient.updateCallType('my-call-type', {
 <TabItem value="py" label="Python">
 
 ```py
-from getstream.models import S3Request
-
 # 1. create a new storage with all the required parameters
-client.create_external_storage(
+from getstream.models.s_3_request import S3Request
+
+client.video.create_external_storage(
     name='my-s3',
     storage_type='s3',
     bucket='my-bucket',
@@ -59,8 +68,12 @@ client.create_external_storage(
     ),
 )
 
-# 2. update the call type to use the new storage
-client.video.update_call_type(name='allhands', external_storage= "my-s3")
+# 2. (Optional) Check storage configuration for correctness
+# In case of any errors, this will throw a StreamAPIException. 
+response = client.video.check_external_storage(name='my-s3')
+
+# 3. update the call type to use the new storage
+client.video.update_call_type(name='allhands', external_storage='my-s3')
 ```
 </TabItem>
 <TabItem value="curl" label="cURL">
@@ -83,7 +96,13 @@ curl -X POST https://video.stream-io-api.com/video/external_storage?api_key=${AP
       }
     }'
 
-# 2. update the call type to use the new storage
+    # 2. (Optional) Check storage configuration for correctness
+curl -X GET https://video.stream-io-api.com/video/external_storage/check?api_key=${API_KEY} \
+    -H "Authorization: ${TOKEN}" \
+    -H "stream-auth-type: jwt"
+
+
+# 3. update the call type to use the new storage
 curl -X PUT https://video.stream-io-api.com/api/v2/video/calltypes/${CALL_TYPE}?api_key=${API_KEY} \
     -H "Authorization: ${TOKEN}" \
     -H "Content-Type: application/json" \