Registers a connected connection_id.

        Args:
            connection_id (str): A unique identifier which identifies an
                connection on the network server socket.
            endpoint (str): The publically reachable endpoint of the new
                peer

def register_peer(self, connection_id, endpoint):
        """Registers a connected connection_id.

        Args:
            connection_id (str): A unique identifier which identifies an
                connection on the network server socket.
            endpoint (str): The publically reachable endpoint of the new
                peer
        """
        with self._lock:
            if len(self._peers) < self._maximum_peer_connectivity:
                self._peers[connection_id] = endpoint
                self._topology.set_connection_status(connection_id,
                                                     PeerStatus.PEER)
                LOGGER.debug("Added connection_id %s with endpoint %s, "
                             "connected identities are now %s",
                             connection_id, endpoint, self._peers)
            else:
                raise PeeringException(
                    "At maximum configured number of peers: {} "
                    "Rejecting peering request from {}.".format(
                        self._maximum_peer_connectivity,
                        endpoint))

        public_key = self.peer_to_public_key(connection_id)
        if public_key:
            self._consensus_notifier.notify_peer_connected(public_key)