refactor: separate API handlers into dedicated packages with improved HTTP utilities (#5127)

pkg/util/http/error.go

@@ -0,0 +1,33 @@
+// Copyright 2025 The frp Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package http
+
+import "fmt"
+
+type Error struct {
+	Code int
+	Err  error
+}
+
+func (e *Error) Error() string {
+	return e.Err.Error()
+}
+
+func NewError(code int, msg string) *Error {
+	return &Error{
+		Code: code,
+		Err:  fmt.Errorf("%s", msg),
+	}
+}