Validation support

### What version of gRPC are you using?
NA

### What did you expect to see?
A provision to validate input data in a meaningful way, preferably using bean validation 2.0 (JSR 380)

My assumption is that currently I have to do adhoc validation for every single request & it defeats the whole purpose of having a framework like bean validation.

Is there any plan to integrate this with bean validation?

The issue names no files, tests, or entry points. Start by reviewing the gRPC Java request-processing path and how Bean Validation 2.0 (JSR 380) could integrate with it. Done would require an agreed framework-level approach to meaningful request validation rather than per-request ad hoc checks.

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