k8s: prep work to uniform annotations style

This is a preparatory commit to the conversion of the annotations to the
xxxxxx.cilium.io/... from, introducing a function to retrieve the value
of an annotation associated with a given key, or one of the additional
aliases if not found.

Signed-off-by: Marco Iorio <[email protected]>

pkg/annotation/k8s.go

@@ -3,6 +3,8 @@
 
 package annotation
 
+import metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+
 const (
 	// Prefix is the common prefix for all annotations
 	Prefix = "io.cilium"
@@ -82,3 +84,16 @@ const (
 	// to that node.
 	WireguardPubKey = Prefix + ".network.wg-pub-key"
 )
+
+// Get returns the annotation value associated with the given key, or any of
+// the additional aliases if not found.
+func Get(obj metav1.Object, key string, aliases ...string) (value string, ok bool) {
+	keys := append([]string{key}, aliases...)
+	for _, k := range keys {
+		if value, ok = obj.GetAnnotations()[k]; ok {
+			return value, ok
+		}
+	}
+
+	return "", false
+}

pkg/annotation/k8s_test.go

@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: Apache-2.0
+// Copyright Authors of Cilium
+
+package annotation
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	corev1 "k8s.io/api/core/v1"
+)
+
+func TestGet(t *testing.T) {
+	var (
+		key     = "key"
+		aliases = []string{"key-alt-1", "key-alt-2"}
+		obj     = corev1.Service{}
+	)
+
+	tests := []struct {
+		name        string
+		annotations map[string]string
+		wantValue   string
+		wantOK      bool
+	}{
+		{
+			"the searched annotation is not present",
+			map[string]string{"other": "other"},
+			"", false,
+		},
+		{
+			"the searched annotation is present (preferred key)",
+			map[string]string{"key": "value", "other": "other"},
+			"value", true,
+		},
+		{
+			"the searched annotation is present (alias)",
+			map[string]string{"key-alt-1": "value-alt-1", "other": "other"},
+			"value-alt-1", true,
+		},
+		{
+			"the searched annotation is present (both preferred and alias keys)",
+			map[string]string{"key": "value", "key-alt-1": "value-alt-1", "other": "other"},
+			"value", true,
+		},
+		{
+			"the searched annotation is present (both alias keys)",
+			map[string]string{"key-alt-1": "value-alt-1", "key-alt-2": "value-alt-2", "other": "other"},
+			"value-alt-1", true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			obj.ObjectMeta.Annotations = tt.annotations
+			value, ok := Get(&obj, key, aliases...)
+			require.Equal(t, tt.wantValue, value)
+			require.Equal(t, tt.wantOK, ok)
+		})
+	}
+}