Sink.completionStageSink
Streams the elements to the given future sink once it successfully completes.
Description
Streams the elements through the given future flow once it successfully completes. If the future fails the stream is failed.
Reactive Streams semantics
cancels if the future fails or if the created sink cancels
backpressures when initialized and when created sink backpressures
1.1.2+29-e21fa9eb*