feat(backend_server.py): add BackendServer._send_ack() helper method

src/judas_server/backend/backend_server.py

@@ -60,6 +60,16 @@ class BackendServer:
                 )
                 time.sleep(1)
 
+    def _send_ack(self, client: Client) -> None:
+        """Send an ACK message to a client.
+
+        Args:
+            client (Client): The client to send the ACK to.
+        """
+        ack: bytes = Message.ack().to_bytes()
+        self.logger.debug(f"[>] Sending ACK to {client}")
+        client.outbound += ack
+
     def _accept_connection(self, sock: socket.socket) -> None:
         """Accept a new client connection.