add option status code log from origin

[t4niwa]

Description

add option status code log from origin

Type of change

• Bug fix
• New feature
• Refactoring (no functional changes, no api changes)
• Non-code changes (update documentation, pipeline, etc.)

Flags

• Breaks backward compatibility
• Requires a documentation update
• Has untestable code

Related issue/PR

Delete this section if there are no issues or pull requests that relate to this pull request.

• Fixes #issue
• Closes #PR

---

Checklist

• Followed the guidelines in the CONTRIBUTING document
• Added prefix [skip ci]/[ci skip]/[no ci]/[skip actions]/[actions skip] in the PR title if necessary
• Tested and linted the code
• Commented the code
• Made corresponding changes to the documentation
• Passed all pipeline checking

Checklist for maintainer

• Use Squash and merge
• Double-confirm the merge message has prefix [skip ci]/[ci skip]/[no ci]/[skip actions]/[actions skip]
• Delete the branch after merge

[WindzCUHK]

@t4niwa
Can help to add a unit test like below?

authorization-proxy/handler/handler_test.go

Lines 519 to 536 in 93fe09a

	{
	name: "check custom transport is used",
	args: args{
	cfg: config.Proxy{
	Transport: config.Transport{
	MaxIdleConnsPerHost: 442,
	},
	},
	},
	checkFunc: func(h http.Handler) error {
	got := h.(*httputil.ReverseProxy).Transport.(*transport).RoundTripper.(*http.Transport).MaxIdleConnsPerHost
	want := 442
	if got != want {
	return errors.Errorf("unexpected MaxConnsPerHost in custom transport, got: %v, want: %v", got, want)
	}
	return nil
	},
	},

Just check when cfg.OriginLog.StatusCode.Enable == true, got.ModifyResponse != nil is OK.

WindzCUHKさん不在のため

[kyfujisa]

↑の指摘事項への対応が行われたことを確認しました。