chore(examples): add one example to log request body when the status code is non 200

[richzw]

References to other Issues or PRs

Add one sample to resolve the issue #3780

Have you read the Contributing Guidelines?

Brief description of what is fixed or changed

One outer wrapper to clone the request body, since the body of the request has been consumed in the customErrorHandler.

Other comments

[johanbrandhorst]

Is this necessary? I don't think the request body should be used after the handler returns.

[richzw]

Is this necessary? I don't think the request body should be used after the handler returns.

Yes, you are right. This line is removed in the new commit. Sorry for the typo.

[johanbrandhorst]

Thanks for the update. Could you perhaps add a small section to the Operations section of our doc with a link to this middleware? Here is the docs site: https://grpc-ecosystem.github.io/grpc-gateway/docs/operations/ and the source is here: https://github.com/grpc-ecosystem/grpc-gateway/tree/main/docs/docs/operations. Just create a new file :).

[richzw]

Thanks for the update. Could you perhaps add a small section to the Operations section of our doc with a link to this middleware? Here is the docs site: https://grpc-ecosystem.github.io/grpc-gateway/docs/operations/ and the source is here: https://github.com/grpc-ecosystem/grpc-gateway/tree/main/docs/docs/operations. Just create a new file :).

The doc has been added. Could you please review this doc? @johanbrandhorst

[johanbrandhorst]

Some minor edits to the doc page, but thank you!

[johanbrandhorst]

Suggested change

	1. `logRequestBody` middleware，which logs the request body when the response status code is not 200.
	1. Create a `http.Handler` middleware. The `logRequestBody` example middleware logs the request body when the response status code is not 200.

[johanbrandhorst]

I think we can be more general than this. How about

Suggested change

	If you want to log the request body in the `customErrorHandler` middleware, unfortunately the request body has been consumed in the `customErrorHandler` middleware and can't be read again. To log the request body, you can use one middleware to buffer the request body before it's consumed.
	If you want to log the request body of incoming requests, you will need to buffer the body before it reaches the gateway. To log the request body, you can use a middleware `http.Handler` to buffer the request body before it's consumed.

[richzw]

I will update the doc

[johanbrandhorst]

Suggested change

	http.Error(w, fmt.Sprintf("grpc server read request body err %+v", err), http.StatusBadRequest)
	http.Error(w, fmt.Sprintf("failed to read body: %v", err), http.StatusBadRequest)

[johanbrandhorst]

Suggested change

	2. Wrap the `logRequestBody` middleware with the `http.ServeMux`:
	2. Wrap the gateway serve mux with the `logRequestBody` handler:

[richzw]

I will fix it

[johanbrandhorst]

Suggested change

	mux := http.NewServeMux()
	mux := runtime.NewServeMux()
	// Register generated gateway handlers

[richzw]

Sorry for the typo

[richzw]

Some minor edits to the doc page, but thank you!

Thank you very much for your detailed review of the document. Could you please review the update comment again? @johanbrandhorst

[johanbrandhorst]

Thanks for your contribution!