Kotlin support

[genuss]

Hi, team!
Let me express my appreciation for this project. I'm glad to see that spring-grpc is becoming part of the official Spring portfolio. I've been following this project for quite some time, and to be honest - I like it more and more. Congratulations on its promotion to a full member!

I'm interested, if there are plans for a better kotlin support. Having tried some basics I found #164 by myself and here. Another issue I found is that kotlin coroutines stubs aren't supported due to lack of a proper StubFactory. I created it and wanted to contribute, but I'd like to ask your opinion on the shape of my change. Putting the new factory in StubFactory's package means that kotlin dependencies must be added to spring-grpc-core artifacts. I guess it's not desirable at least at the moment. That's why I'm asking a couple of questions:

• Do you plan for better kotlin support?
• How would you implement it: a separate artifact like spring-grpc-kotlin, a number of artifacts for client and server, or directly in spring-grpc-core with optional kotlin dependencies?

With these questions answered it would be possible to kickstart some development. I've already got a couple of features on my mind: coroutine stubs, suspending exception handlers, etc.

[dsyer]

Better Kotlin support would be nice. You can look at some other projects (Spring Framework, Spring Boot, Spring Cloud Function probably the best since it is a Maven build) to see how Kotlin support has been added - probably a separate jar file makes sense for the core features at least. It's not a big thing, but finding people to contribute and maintain Kotlin features is often a challenge. So send a PR and then stick around, please, if you can.

[genuss]

I believe it may be closed now. Thanks for your answer!
With #169 and #173 the basics are done. I'll keep investigating kotlin-related cases and come back if needed

[dsyer]

Thanks. Please keep sending new features. If we need a new jar file at some point we can do it that way.