Defer the creation of a
Source/Flow until materialization and access
setup operator has been deprecated, use fromMaterializer instead.
def setup[T, M](factory: (ActorMaterializer, Attributes) => Source[T, M]): Source[T, Future[M]]
def setup[T, U, M](factory: (ActorMaterializer, Attributes) => Flow[T, U, M]): Flow[T, U, Future[M]]
Typically used when access to materializer is needed to run a different stream during the construction of a source/flow. Can also be used to access the underlying