=str #15152 ast transformations

* for feedback
* only supports Flow map operation
As per [this comment](https://github.com/akka/akka/blob/f3225473ff04aeaffcc00d3e84d849621b6884ed/akka-stream/src/main/scala/akka/stream/scaladsl/FlowGraph.scala#L472-L473) this method has to return instance that is uniquely identifyable. So name should be dropped, but you are right saying that dispatcher and buffer attributes can be kept.

It seems that we need one more attribute (e.g. Description) which would not be involved in Vertex equality and actor names.