Support logging Authorization User

For reqeust with Authorization header or Proxy-Authorization header,
the user name is not stored in the URL. So the logger will not output
it.

In order to log user name for Authorization, we could update the User
filed of http.Request. So the logger should use the latest value.

logging.go

@@ -52,6 +52,10 @@ func (h loggingHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 		}
 	}
 
+	if url.User != req.URL.User {
+		url.User = req.URL.User
+	}
+
 	params := LogFormatterParams{
 		Request:    req,
 		URL:        url,

logging_test.go

@@ -129,6 +129,22 @@ func TestLogPathRewrites(t *testing.T) {
 	}
 }
 
+func TestLogUser(t *testing.T) {
+	var buf bytes.Buffer
+
+	handler := http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+		req.URL.User = url.User("foo")
+		w.WriteHeader(http.StatusOK)
+	})
+	logger := LoggingHandler(&buf, handler)
+
+	logger.ServeHTTP(httptest.NewRecorder(), newRequest(http.MethodGet, "/"))
+
+	if !strings.Contains(buf.String(), "- foo [") {
+		t.Fatalf("Got log %#v, wanted substring %#v", buf.String(), "- foo [")
+	}
+}
+
 func BenchmarkWriteLog(b *testing.B) {
 	loc, err := time.LoadLocation("Europe/Warsaw")
 	if err != nil {