title: spring-cloud-stream request-reply messaging pattern
body: <p>Is there a request-reply pattern that one should use with spring-cloud-stream? All the documentation I can find on spring-cloud-stream is geared toward the MessageChannel.send fire-and-forget type of producer, and I'm familiar with @MessagingGateway from spring-integration, but I'm not sure how that would work with spring-cloud-stream. That would be useful when you have a REST POST endpoint that saves an entity with an assigned identifier and you need to return the assigned identifier to the caller, but you still want to use messaging.</p>