Allow specifying validators in grpc_api_configuration sidecar file

[v3n]

grpc_api_configuration is a sidecar .yml file allowing for specifying varying API configurations outside of the .proto file. It would be awesome if go-proto-validators could generate validators for a gRPC configuration based on this, so that clients don't have to include go-proto-validators in a non-Go project.

To take the example on the README.

package validator.examples;
import "github.com/mwitkow/go-proto-validators/validator.proto";

message InnerMessage {
  // some_integer can only be in range (1, 100).
  int32 some_integer = 1 [(validator.field) = {int_gt: 0, int_lt: 100}];
  // some_float can only be in range (0;1).
  double some_float = 2 [(validator.field) = {float_gte: 0, float_lte: 1}];
}

Could be specified as:

validators:
  - selector: validator.examples.InnerMessage
    fields:
      - selector: some_integer
        field:
          int_gt: 0
          int_lt: 100
      - selector: some_float
        field:
          int_gt: 0
          int_lte: 1