get metadata from REST channel

changelog/11311.bugfix.md

@@ -0,0 +1 @@
+Re-instates the REST channel metadata feature. Metadata can be provided on the `metadata` key.

docs/docs/connectors/your-own-website.mdx

@@ -82,7 +82,10 @@ After making the `callback` input available, you can `POST` messages to
 ```json
 {
   "sender": "test_user",  // sender ID of the user sending the message
-  "message": "Hi there!"
+  "message": "Hi there!",
+  "metadata": {           // optional metadata
+    "key1": "value1"
+  }
 }
 ```
 

rasa/core/channels/rest.py

@@ -58,6 +58,21 @@ def _extract_message(self, req: Request) -> Optional[Text]:
     def _extract_input_channel(self, req: Request) -> Text:
         return req.json.get("input_channel") or self.name()
 
+    def get_metadata(self, request: Request) -> Optional[Dict[Text, Any]]:
+        """Extracts additional information from the incoming request.
+
+         Implementing this function is not required. However, it can be used to extract
+         metadata from the request. The return value is passed on to the
+         ``UserMessage`` object and stored in the conversation tracker.
+
+        Args:
+            request: incoming request with the message of the user
+
+        Returns:
+            Metadata which was extracted from the request.
+        """
+        return request.json.get("metadata", None)
+
     def stream_response(
         self,
         on_new_message: Callable[[UserMessage], Awaitable[None]],
@@ -66,6 +81,21 @@ def stream_response(
         input_channel: Text,
         metadata: Optional[Dict[Text, Any]],
     ) -> Callable[[Any], Awaitable[None]]:
+        """Streams response to the client
+
+         If the stream option is enabled, this method will be called to
+         stream the response to the client
+
+        Args:
+            on_new_message: sanic event
+            text: message text
+            sender_id: message sender_id
+            input_channel: input channel name
+            metadata: optional metadata sent with the message
+
+        Returns:
+            Sanic stream
+        """
         async def stream(resp: Any) -> None:
             q: Queue = Queue()
             task = asyncio.ensure_future(