Source generated actor clients

[philliphoff]

Description

Adds a .NET source generator that can be used to generate strongly-typed clients for interacting with actors, per proposal in #1158.

Changes include:

• Adds a separate Dapr.Actors.Generators NuGet package that contains the source generator
• Adds a unit test project, Dapr.Actors.Generators.Test for the source generator
• Adds a separate E2E test project Dapr.E2E.Test.Actors.Generators
• Adds a new example for using the source generator

Strongly-typed clients are generated by:

1. Referencing the Dapr.Actors.Generators NuGet package.

   <Project>
     <ItemGroup>
        <PackageReference Include="Dapr.Actors.Generators" Version="x.x.x" />
     </ItemGroup>
   </Project>

2. Add the Dapr.Actors.Generators.GenerateActorClientAttribute to the actor interface.

   using Dapr.Actors.Generators;
   
   namespace Sample;
   
   internal sealed record SampleState(string Value);
   
   [GenerateActorClient]
   internal interface ISampleActor
   {
       [ActorMethod(Name = "GetState")]
       Task<SampleState> GetStateAsync(CancellationToken cancellationToken = default);
   
       [ActorMethod(Name = "SetState")]
       Task SetStateAsync(SampleState state, CancellationToken cancellationToken = default);
   }

   The Dapr.Actors.Generators.ActorMethodAttribute can be used to map interface methods definitions to specific actor methods should the names differ (e.g. the interface uses "Async" suffix common in .NET but the actor methods do not).

3. A strongly-typed client will be generated that can be used to invoke actor methods.

   using Dapr.Actors;
   using Dapr.Actors.Client;
   using Sample;
   
   var proxy = ActorProxy.Create(ActorId.CreateRandom(), "SampleActor");
   
   using var cancellationTokenSource = new CancellationTokenSource(TimeSpan.FromSeconds(30));
   
   var client = new SampleActorClient(proxy);
   
   var state = await client.GetStateAsync(cancellationTokenSource.Token);
   
   await client.SetStateAsync(new SampleState("Hello, World!"), cancellationTokenSource.Token);

Issue reference

We strive to have all PR being opened based on an issue, where the problem or feature have been discussed prior to implementation.

Please reference the issue this PR will close: #1158

Checklist

Please make sure you've completed the relevant tasks for this PR, out of the following list:

• Code compiles correctly
• Created/updated tests
• Extended the documentation

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (e244e88) 67.28% compared to head (cb28b7e) 67.28%.
Report is 1 commits behind head on master.

Additional details and impacted files

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  Coverage   67.28%   67.28%           
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  Files         174      174           
  Lines        6025     6025           
  Branches      671      671           
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  Hits         4054     4054           
  Misses       1802     1802           
  Partials      169      169           

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net6	67.26% <ø> (ø)
net7	67.26% <ø> (ø)
net8	67.27% <ø> (ø)

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[halspang]

@philliphoff - Is this still a WIP or is it ready for review?

[philliphoff]

@halspang It's ready for review, assuming the parent proposal is accepted without significant changes. (Happy to have feedback, but I know the maintainers have been busy with other things.)

And I'll need to look into the CI failures.

[philliphoff]

The remaining integration test failures seems to be a preexisting flaky actor timer test. (It's also failing for PRs that make no code changes.)

[halspang]

Overall, this looks great. Not super familiar with code generation, but it makes sense as presented. Just a few questions but nothing really blocking except maybe the testing just to avoid duplication.