[REQ] [Dart] Consider StreamController or RxDart for (de)serialization json

If possible, instead of (de)materializing json in memory, consider the use of StreamController combined with StreamTransformer to (de)serialize json.

Or with RxDart, for example:

    var dataStreamFromAPI = new PublishSubject<String>();

    dataStreamFromAPI
        .map<User>((jsonString) => User.fromJson(jsonString))
        .listen((user) => print(user.toString()));

More RxDart examples: https://www.burkharts.net/apps/blog/rxdart-magical-transformations-of-streams/

This would benefit the processing of larger json payloads and overall performance.

Begin by identifying the Dart client's current JSON serialization and deserialization entry points, then review the proposed StreamController, StreamTransformer, and RxDart approaches. Define how large payloads should be processed without materializing them in memory, and consider how performance and completion criteria would be tested.