Introduce message kinds, and handle them appropriately in user and agent chat

backend/server.py

@@ -185,8 +185,11 @@ def start_server(app):
                 elif action == "send-chat-message":
                     message = app.send_chat_message(
                         chat_id=body['chatId'],
-                        content=body['content'],
                         thread_id=body.get('threadId'),
+                        content=body['content'],
+                        kind=body.get('kind'),
+                        subkind=body.get('subkind'),
+                        format=body.get('format'),
                     )
                     await send({'message': "message sent", 'messageId': message['id'], 'nonce': nonce})