Message pack marshaller/custom fomatters

[max-ieremenko]

ServiceModel.Grpc.MessagePackMarshaller should support AOT builds.

dotnet publish some-project.csproj

<PropertyGroup>
  <TargetFramework>net8.0</TargetFramework>
  <PublishAot>true</PublishAot>
</PropertyGroup>

<ItemGroup>
  <PackageReference Include="ServiceModel.Grpc.MessagePackMarshaller" />
</ItemGroup>

[MessagePackObject]
class SomeObject {}

[OperationContract]
Task<SomeObject> PingPong(SomeObject value);

IL code-generation is not the case, all required code should be generated during the build time. Extend ServiceModel.Grpc.DesignTime and ServiceModel.Grpc.MessagePackMarshaller to support MessagePack custom formaters.

<ItemGroup>
   <!-- reference c# code generators -->
  <PackageReference Include="ServiceModel.Grpc.DesignTime" />
</ItemGroup>

[ImportGrpcService(typeof(IService))] // instruct ServiceModel.Grpc.DesignTime to generate required code during the build process
[MessagePackDesignTimeExtension]  // instruct ServiceModel.Grpc.MessagePackMarshaller to generate required code during the build process
internal static partial class MyGrpcServices {}

Behind the scene required custom formaters should be created and registered for use with MessagePackMarshallerFactory