The `replyTo` must be mandatory for the `RpcServer`

[artembilan]

Describe the bug

The AmqpRpcServer has this logic:

this.publisher = this.connection.publisherBuilder().build();

So, Publisher is configured without toAddress.
Then we have this in its consumer logic:

                  Message reply = handler.handle(context, msg);
                  if (reply != null && msg.replyTo() != null) {
                    reply.to(msg.replyTo());
                  }

So, if no msg.replyTo(), then no toAddress in the end.
I guess we would fail on publishing reply, but do we really need even try?
Feels like better to fail fast here and ask for msg.replyTo() property being provided in request.

Reproduction steps

Consume requests via RpcServer when they don't have replyTo property.

Expected behavior

The RpcServer should fail fast on consumed request if that does not replyTo property.

Additional context

I might be wrong in analysis, so any clarification in the behavior would be great.
Thanks

[acogoluegnes]

Your analysis is correct, the reply won't go anywhere if the to field is not set. It could be set with a custom replyPostProcessor (not done by the default one). I added a reply.to() != null check before sending the reply, thanks for looking into that.