!str #19732 Concise and consistent way to mark async boundaries

akka-docs/rst/scala/code/docs/stream/FlowDocSpec.scala

@@ -237,11 +237,8 @@ class FlowDocSpec extends AkkaSpec {
 
   "defining asynchronous boundaries" in {
     //#flow-async
-    import akka.stream.Attributes.asyncBoundary
-
     Source(List(1, 2, 3))
-      .map(_ + 1)
-      .withAttributes(asyncBoundary)
+      .map(_ + 1).async
       .map(_ * 2)
       .to(Sink.ignore)
     //#flow-async

akka-docs/rst/scala/code/docs/stream/MigrationsScala.scala

@@ -23,6 +23,11 @@ class MigrationsScala extends AkkaSpec {
           })
         })
         //#expand-state
+
+        //#async
+        val flow = Flow[Int].map(_ + 1)
+        Source(1 to 10).via(flow.async)
+        //#async
       }
     }
   }