swagger: Prefix used in nested-field GET params does not respect json_names_for_fields

[jgiles]

Steps you follow to reproduce the error:

1. Create proto structure like this:

message TimestampRange {
    google.protobuf.Timestamp after = 1;
    google.protobuf.Timestamp before = 2;
}
message GetFoosRequest {
    TimestampRange created_at = 1;
    string other_filter = 2;
}

service Foo {
    rpc GetFoos (GetFoosRequest) returns (GetFoosResponse) {
        option (google.api.http) = {
            get: "/v1/foos"
        };
    }
}

2. Run protoc-gen-swagger with json_names_for_fields=true
3. Observe generated Swagger parameter list like

"parameters": [
          {
            "name": "created_at.after",
            "in": "query",
            "required": false,
            "type": "string",
            "format": "date-time"
          },
          {
            "name": "created_at.before",
            "in": "query",
            "required": false,
            "type": "string",
            "format": "date-time"
          },
          {
            "name": "otherFilter",
            "in": "query",
            "required": false,
            "type": "string"
          },
]

What did you expect to happen instead:

The GET parameter should be createdAt.after.

What's your theory on why it isn't working:

Prefix assembly uses field.GetName() without checking GetUseJSONNamesForFields here:

grpc-gateway/protoc-gen-swagger/genswagger/template.go

Line 204 in e16fcd4

p, err := queryParams(msg, nestedField, prefix+field.GetName()+".", reg, pathParams)

[jgiles]

@johanbrandhorst I went ahead and put up #1126 for this (with a test case).