Get the messages of the chat thread with the given ID.
Args:
thread_id (str): The .thread_id of the chat thread
limit__last_n (int | None): Limit to the last N messages
offset (int | None): Offset for pagination
approved_user (User): The current approved user
Returns: Dict containing the messages of the chat thread
The access token received from the authorization server in the OAuth 2.0 flow.