GenerateFile generates the jsonpb/protojson marshaler implementations for every Message in the input proto file.

GenerateHeader generates the header comments, which contain information about the build tools and arguments.

GenerateMarshalers generates the actual MarshalJSON implementations for each Message in the input file.

Options represents the flags passed to protoc-gen-go-json via the protoc command line.

GeneratedFile is the set of methods needed by protoc-gen-go-json on *protogen.GeneratedFile.