Implemented Service Endpoint Registration using Source Generation

[adamreed90]

This is an example of implementing a Source Generated Service Endpoint helper for registering endpoints using Attributes.

See the example project in tests/EndpointRegistrationTest

Usage:

await using var nats = new NatsConnection();
var svc = new NatsSvcContext(nats);
await svc.AddEndpointControllers();

Declarations:

[NatsServiceController(Name = "Name", Version = "Version", QueueGroup = "QueueGroup")]
public class PingController : NatsServiceControllerBase
{
    [NatsServiceEndpoint("Ping", "Subject", "QueueGroup")]
    public async ValueTask Ping(NatsSvcMsg<string> arg)
    {
        if (arg.Data == "Ping!")
            await arg.ReplyAsync("Pong!");
    }
}

[adamreed90]

Still working at this, updated my example, some issues I've had so far are that Attributes can't support the use of Metadata and Serializer configuration as those types aren't supported in attributes.

[adamreed90]

@rickdotnet Have a look at this, something I'm working on.

[adamreed90]

Hoping to get back to work on this at the end of the month, had some things come up.