feat: implement negotiation

By implementing SocketBase and adding the socket to the state, the negotiation will automatically give the right endpoints.

ref: N25B-168

src/robot_interface/endpoints/receiver_base.py

@@ -15,7 +15,7 @@ class ReceiverBase(SocketBase, object):
         :param message: The message to handle.
         :type message: dict
 
-        :return: A response message.
-        :rtype: dict
+        :return: A response message or None if this type of receiver doesn't publish.
+        :rtype: dict | None
         """
-        return {"endpoint": "error", "data": "The requested receiver is not implemented."}
+        raise NotImplementedError()