Fix: Keep original name of field

[tigh-latte]

Currently, if I have the following .proto file:

// The request message containing the user's name.
message HelloRequest {
  string my_name = 1;
}

And the following stub:

{
    "service": "helloworld.Greeter",
    "method": "SayHello",
    "in": {
        "equals": {
            "my_name": "hi"
        }
    },
    "out": {
        "data": {
            "message": "lemon"
        }
    }
}

And I were to make the following request:

grpc -plaintext -d @ 0.0.0.0:22222 helloworld.Greeter/SayHello <<! | jq
{
	"my_name": "hi"
}
!

The mock server would fail to match the stub to the request, because once data is parsed into its internal map m, it's converted to camelCase and instead searches for "myName": "hi". The GRPC services I work with have snake cased fields, so when mocking, the the in's must be camel, and the outs must be snake.

I propose doing this, having a jsonpb marshaller which marshels the keynames down to the original name defined in the .proto file, to allow the above scenario to pass.

[theflyingcodr]

Hi, will this be merged?

[tigh-latte]

I've another PR to open for this branch too to add header support @theflyingcodr , since the container you guys use has both of these changes implemented.