Props methods for propagating and setting IActorProducer are pretty weird

[Aaronontheweb]

Akka.NET Version: v1.3.9

This is how we set the ActorProducer inside Props today when we're using dependency injection:

akka.net/src/core/Akka/Actor/Props.cs

Lines 292 to 298 in 3c6115e

	public Props(Deploy deploy, Type type, params object[] args)
	{
	Deploy = deploy;
	inputType = type;
	Arguments = args;
	producer = CreateProducer(inputType, Arguments);
	}

It's indirect, and we repeat this process of using reflection on the input type to figure out if we should use a custom ActorProducer whenever someone calls any of the fluent interface methods on Props, all of which end up calling the Props.Copy() method:

akka.net/src/core/Akka/Actor/Props.cs

Lines 583 to 586 in 3c6115e

	protected virtual Props Copy()
	{
	return new Props(Deploy, inputType, Arguments) { SupervisorStrategy = SupervisorStrategy };
	}

I'm not sure why we designed it this way, but it's gross, relies on magic, and not all that extensible. What irks me most about it is that the Type we feed into Props can mean different things other than the actor's implementation. I'd rather change the signatures on Props to make it 100% explicit "I AM USING THIS PRODUCER" and not let the arguments of various Props constructors take on different meanings for the same input.

How we do this without breaking 100% of existing DI plugins for Akka.NET is an interesting question. I guess a reasonable way of handling that is just "upgrade all of them" since this change doesn't have a meaningful impact on end-user code today, but it would break binary compatibility since fixing this issue might end up changing either the signatures of existing Props methods or changing their meanings. That doesn't seem like a big deal.

[Aaronontheweb]

Going to put this into the v1.4.0 branch, since this will probably require an update to all of the Akka.DI.* plugins.