Create util for etcdctl, move helper of cobra from main package to

etcdctl util, create normalizer of examples in util, add some more
examples, change indent of etcdctl from "\t" to "  "

Signed-off-by: ah8ad3 <ah8ad3@gmail.com>

etcdctl/util/normalizer.go

@@ -0,0 +1,49 @@
+// Copyright 2024 The etcd 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 util
+
+import "strings"
+
+const indentation = "  "
+
+// Normalize normalizes a string:
+//  1. trim the leading and trailing space
+//  2. add an indentation before each line
+func Normalize(s string) string {
+	if len(s) == 0 {
+		return s
+	}
+	return normalizer{s}.trim().indent().string
+}
+
+type normalizer struct {
+	string
+}
+
+func (n normalizer) trim() normalizer {
+	n.string = strings.TrimSpace(n.string)
+	return n
+}
+
+func (n normalizer) indent() normalizer {
+	indentedLines := []string{}
+	for _, line := range strings.Split(n.string, "\n") {
+		trimmed := strings.TrimSpace(line)
+		indented := indentation + trimmed
+		indentedLines = append(indentedLines, indented)
+	}
+	n.string = strings.Join(indentedLines, "\n")
+	return n
+}