[Broker] multi-topic subscriptions

If a broker endpoint subscribes to multiple topics, how many messages do
you expect to receive? Consider this snippet:

  context ctx;
  auto e = ctx.spawn<blocking>();
  e.publish("/foo/bar/baz", 4.2);

Should the endpoint receive exactly one message or the same message
three times? Personally, I think use exactly-once delivery semantics
would be most intuitive.


Yeah, seems most intuitive to me too.