docs: add example to fully override http responses

[nguyentranbao-ct]

Updates the documentation to include an example of fully overriding custom HTTP responses using a Forward Response Option and a Custom Marshaller.

References to other Issues or PRs

Not actually a fix, but a guide that partially supports #4483

Have you read the Contributing Guidelines?

Yes

Brief description of what is fixed or changed

• Provided an example with CreateUserResponse proto message.
• Demonstrated setting up gRPC-Gateway with custom options.
• Included a forwardResponse function and a custom marshaller ResponseWrapper.

[johanbrandhorst]

Thanks for this, just a few comments!

[johanbrandhorst]

Nit: I think the spelling is Mashaler in the Go ecosystem

Suggested change

	To fully override custom HTTP responses, you can use both a Forward Response Option and a Custom Marshaller.
	To fully override custom HTTP responses, you can use both a Forward Response Option and a Custom Marshaler.

[johanbrandhorst]

Suggested change

	Create a custom marshaller to format the response data which utilizes the builtin JSON marshaller:
	Create a custom marshaler to format the response data which utilizes the builtin JSON marshaler as a fallback:

[johanbrandhorst]

I think you may want to use c.JSONPb.Marshal? It's important to use a protobuf-aware JSON marshaler with protobuf types.

Suggested change

	return json.Marshal(resp)
	return c.JSONPb.Marshal(resp)

[johanbrandhorst]

I think this should embed runtime.JSONPb to make sure it supports protobuf messages in general (the behavior will differ around things like enums, oneofs, etc). See https://pkg.go.dev/github.com/grpc-ecosystem/grpc-gateway/v2/runtime#JSONPb.

[nguyentranbao-ct]

Fixed, I’d like to add our company to the adopters list too, if that’s alright.

[johanbrandhorst]

Awesome, thanks!