refactor(backend_server.py): use _send_ack() in _handle_connection()

src/judas_server/backend/backend_server.py

@@ -150,10 +150,7 @@ class BackendServer:
                             f"[<] Complete message from {client}: {line!r}"
                         )
 
-                    # send ACK
-                    ack = Message.ack().to_bytes()
-                    self.logger.debug(f"[>] Sending ACK to {client}")
-                    client.outbound += ack
+                    self._send_ack(client)
 
                     # set last seen
                     client.last_seen = time.time()