@Nullable public Endpoint remoteEndpoint() {
    return remoteEndpoint;
  }
When an RPC (or messaging) span, indicates the other side of the connection.

<p>By recording the remote endpoint, your trace will contain network context even if the peer
is not tracing. For example, you can record the IP from the {@code X-Forwarded-For} header or
the service name and socket of a remote peer.
zipkin/src/main/java/zipkin2/Span.java