* GH-2729: Reactor Kafka Binder SenderResult Support Resolves https://github.com/spring-cloud/spring-cloud-stream/issues/2729 Allow configuration of a `FluxMessageChannel` to receive `SenderResult`s. Add `SenderResultMessageHandler` to consume from that channel. Remove undocumented `sendResult` header, which has no value without the sender result correlation metadata. * Add integration test and polish property docs. - result channel must be FMC for reactive binder. * Add documentation. * Remove SenderResultMessageHandler.