feat(backend_server.py): add warning if received an unknown message (no handler)

src/judas_server/backend/backend_server.py

@@ -274,7 +274,7 @@ class BackendServer:
                                     f"First message from {client} must be HELLO, disconnecting..."
                                 )
                                 self._disconnect(client)
-                                return
+                                continue
 
                         handler: Callable[[Client, Message], None] | None = (
                             self.message_handlers.get(
@@ -283,6 +283,11 @@ class BackendServer:
                         )
                         if handler is not None:
                             handler(client, msg)
+                        else:
+                            self.logger.warning(
+                                f"No handler for message {msg.id} with category {msg.category} and action {msg.action}"
+                            )
+                            continue
 
                         if msg.ack_required:
                             self.send_ack(client, target_id=msg.id)