Use github.com/grpc-ecosystem/go-grpc-middleware/validator

[rvolosatovs]

Let's generate validators using this package, that should be possible, no @htdvisser ? https://github.com/grpc-ecosystem/go-grpc-middleware/tree/master/validator

[htdvisser]

After a quick look at the proposed package, I think it's a bit too simple (at the moment). We don't just have strings and numbers, but use custom types with custom validation.

Also, I already started working on validations: https://github.com/TheThingsNetwork/api/compare/feature/go-validate

[htdvisser]

Iceboxing this for now