=str #15900 Make fanout publisher actor name unique
=str #15892 Fix ClassCastException in ThunkSource

* and add test
Merge pull request #15994 from akka/wip-15892-ClassCastException-ThunkSource-patriknw

=str #15892 Fix ClassCastException in ThunkSource
Merge pull request #15997 from akka/wip-15900-fanout-actor-name-patriknw

=str #15900 Make fanout publisher actor name unique
+str #15996 Add mapAsyncUnordered

* rename mapFuture to mapAsync
* add mapAsyncUnordered
* extract common things for emits to a trait
Merge pull request #15999 from akka/wip-15996-unordered-mapFuture-patriknw

+str #15996 Add unorderedMapAsync
+str #15960 Correction of FlowGraph variance