Move inmemoryresponsewriter into own package

Kubernetes-commit: f67e15a26f5958b1ebf07a2590e98889a987677d

pkg/util/responsewriter/inmemoryresponsewriter.go

@@ -0,0 +1,70 @@
+/*
+Copyright 2024 The Kubernetes 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 responsewriter
+
+import (
+	"fmt"
+	"net/http"
+)
+
+// inMemoryResponseWriter is a http.Writer that keep the response in memory.
+type inMemoryResponseWriter struct {
+	writeHeaderCalled bool
+	header            http.Header
+	respCode          int
+	data              []byte
+}
+
+func NewInMemoryResponseWriter() *inMemoryResponseWriter {
+	return &inMemoryResponseWriter{header: http.Header{}}
+}
+
+func (r *inMemoryResponseWriter) Header() http.Header {
+	return r.header
+}
+
+func (r *inMemoryResponseWriter) RespCode() int {
+	return r.respCode
+}
+
+func (r *inMemoryResponseWriter) Data() []byte {
+	return r.data
+}
+
+func (r *inMemoryResponseWriter) WriteHeader(code int) {
+	r.writeHeaderCalled = true
+	r.respCode = code
+}
+
+func (r *inMemoryResponseWriter) Write(in []byte) (int, error) {
+	if !r.writeHeaderCalled {
+		r.WriteHeader(http.StatusOK)
+	}
+	r.data = append(r.data, in...)
+	return len(in), nil
+}
+
+func (r *inMemoryResponseWriter) String() string {
+	s := fmt.Sprintf("ResponseCode: %d", r.respCode)
+	if r.data != nil {
+		s += fmt.Sprintf(", Body: %s", string(r.data))
+	}
+	if r.header != nil {
+		s += fmt.Sprintf(", Header: %s", r.header)
+	}
+	return s
+}