Ability to customize gRPC server's fallbackHandlerRegistry

[vladykin]

Description

I'm looking for a way to set the fallbackHandlerRegistry for a gRPC server created by Quarkus.

Need it to customize handling of the gRPC calls that the server doesn't implement, in particular:

• log such calls;
• attach custom trailers to the UNIMPLEMENTED response.

Normally, I'd use a gRPC server interceptor for both logging and adding trailers. But server interceptors are not called for unimplemented methods.

Related: #10039

Implementation ideas

No response

[quarkus-bot]

/cc @alesj (grpc), @cescoffier (grpc)