Support .map() that returns ResponseStream instead of Stream

[maherjaafar]

keeping the return type as `ReponseStream` to be able to call **.cancel()** after using `.map()` Used version: `grpc: 3.2.4` ## Example ``` final myStream = _client .myReponseStream .listen((event) => event.map((event) => event.value)); ``` Expected result: I expect to get result of type `ReponseStream` but the result will be of type `Stream` Actual result: `Stream`

[maherjaafar]

Any updates?

[maherjaafar]

@mosuem any updates?

[mosuem]

Hi @maherjaafar, I am not sure what you mean. Where does this WatchEventsRequest come from?

[maherjaafar]

@mosuem It's just an example. I changed it⬆️

The issue arises when I use .map, as it converts it to a Stream instead of a ResponseStream. Consequently, I lose the ability to call myResponseStream.cancel() to cancel the stream.