Better integration with Akka.DependencyInjection

[Aaronontheweb]

Changes

close #144 - working on improving the accessibility of the IDependencyResolver from Akka.DependencyInjection inside all methods responsible for instantiating actors.

Checklist

For significant changes, please ensure that the following have been completed (delete if not relevant):

• This change follows the Akka.NET API Compatibility Guidelines.
• This change follows the Akka.NET Wire Compatibility Guidelines.
• I have reviewed my own pull request.
• Design discussion issue Tighter integration with Extensions.DependencyInjection #144
• Changes in public API reviewed, if any.
• I have added website documentation for this feature.

[Aaronontheweb]

So we have some neat new APIs now to close out #144

Actors in General

// arrange
using var host = await StartHost(collection =>
{
    collection.AddAkka("MyActorSys", (builder, sp) =>
    {
        builder.WithActors((system, registry, resolver) =>
        {
            var singletonActor = system.ActorOf(resolver.Props<SingletonActor>(), "singleton");
            registry.TryRegister<SingletonActor>(singletonActor);
        });
    });
});

// act
var singletonInstance = host.Services.GetRequiredService<IMySingletonInterface>();
var singletonActor = host.Services.GetRequiredService<ActorRegistry>().Get<SingletonActor>();
var singletonFromActor =
    await singletonActor.Ask<IMySingletonInterface>(SingletonActor.GetSingleton.Instance, TimeSpan.FromSeconds(3));

// assert
singletonFromActor.Should().Be(singletonInstance);

The third parameter on this new overload for WithActors is an IDependencyResolver, so working with DI is now just a matter of picking the configuration delegate you wish to use.

Akka.Cluster.Sharding

All of the ShardRegion overloads also support IDependencyResolver now as well:

public static AkkaConfigurationBuilder WithShardRegion<TKey>(
    this AkkaConfigurationBuilder builder,
    string typeName,
    Func<ActorSystem, IActorRegistry, IDependencyResolver, Func<string, Props>> entityPropsFactory,
    IMessageExtractor messageExtractor,
    ShardOptions shardOptions)
{
    return builder.WithShardRegion<TKey>(typeName, entityPropsFactory,
        messageExtractor.ToExtractEntityId(), messageExtractor.ToExtractShardId(), shardOptions);
}

We now accept an overload for creating the entity actor Props that accesses the current ActorSystem, ActorRegistry, and the DependencyResolver.

Akka.Cluster.Tools.Singleton

We now accept an overload for creating the singleton actor Props that accesses the current ActorSystem, ActorRegistry, and the DependencyResolver.

(don't mind the testing infrastructure)

protected override void ConfigureServices(HostBuilderContext context, IServiceCollection services)
{
    services.AddSingleton<IMyThing>(new ThingImpl("foo1"));
    base.ConfigureServices(context, services);
}

protected override void ConfigureAkka(AkkaConfigurationBuilder builder, IServiceProvider provider)
{
    builder.ConfigureHost(configurationBuilder =>
    {
        configurationBuilder.WithSingleton<MySingletonDiActor>("my-singleton",
            (_, _, dependencyResolver) => dependencyResolver.Props<MySingletonDiActor>());
    },  new ClusterOptions(){ Roles = new[] { "my-host" }}, _tcs, Output!);
}

[Fact]
public async Task Should_launch_ClusterSingletonAndProxy_with_DI_delegate()
{
    // arrange
    await _tcs.Task; // wait for cluster to start

    var registry = Host.Services.GetRequiredService<ActorRegistry>();
    var singletonProxy = registry.Get<MySingletonDiActor>();
    var thing = Host.Services.GetRequiredService<IMyThing>();

    // act
    
    // verify round-trip to the singleton proxy and back
    var respond = await singletonProxy.Ask<string>("hit", TimeSpan.FromSeconds(3));

    // assert
    respond.Should().Be(thing.ThingId);
}

I think this should make it a lot easier to use Akka.DependencyInjection going forward. I hope you agree @kpko

[Aaronontheweb]

Completed a self-review of changes

[Aaronontheweb]

Decided to use the Akka.Hosting.TestKit in some places.

[Aaronontheweb]

Validate that we can start singletons with DI and resolve dependencies correctly afterwards

[Aaronontheweb]

Refactored TestHelper in order to use it with the Akka.Hosting.TestKit

[Aaronontheweb]

I got an error inside Akka.Cluster.Hosting.Tests claiming that this assembly (Microsoft.Bcl.AsyncInterfaces) could not be found, so I added it to the TestKit project. If this was an err I can try adding it to the tests and not the shared library. I added it to the library because I suspected that other users might run into this problem.

Amazingly enough, I've used the TestKit package in my own apps (which also target .NET 6.0) and never ran into this problem. I assumed that the problem in this solution was that Akka.Hosting.TestKit targets .NET Standard 2.0.

[Arkatufus]

Microsoft.Bcl.AsyncInterfaces have a severe backward compatibility with netstandard2.0 target, I had to write my own .FirstOrDefault() in Discovery.Azure to avoid that problem.

[Aaronontheweb]

Standardized creation of ClusterShardingSettings

[Aaronontheweb]

Original cluster singleton API - now calls the new method under the covers.

[Aaronontheweb]

Integration test for basic actor DI support

[Aaronontheweb]

C# cleanup

[Aaronontheweb]

new delegate type, since I didn't want to break backwards compat with everyone using the original ActorStarter (even though we're working on maturing the API). I didn't see any harm in adding a new delegate type here.

[Aaronontheweb]

New overloads for exposing the IDependencyResolver to users.

[Arkatufus]

LGTM