cli: create backups for CRDs and their resources

These backups could be used in case an upgrade
misbehaves after helm declared it as successful.
The manual backups are required as helm-rollback
won't touch custom resources and changes to CRDs
delete resources of the old version.

internal/kubernetes/kubectl/kubectl_test.go

@@ -0,0 +1,46 @@
+/*
+Copyright (c) Edgeless Systems GmbH
+
+SPDX-License-Identifier: AGPL-3.0-only
+*/
+
+package kubectl
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestParseCRDs(t *testing.T) {
+	testCases := map[string]struct {
+		data    string
+		wantErr bool
+	}{
+		"success": {
+			data:    "apiVersion: apiextensions.k8s.io/v1\nkind: CustomResourceDefinition\nmetadata:\n  name: nodeimages.update.edgeless.systems\nspec:\n  group: update.edgeless.systems\n  names:\n    kind: NodeImage\n",
+			wantErr: false,
+		},
+		"wrong kind": {
+			data:    "apiVersion: v1\nkind: Secret\ntype: Opaque\nmetadata:\n  name: supersecret\n  namespace: testNamespace\ndata:\n  data: YWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWE=\n",
+			wantErr: true,
+		},
+		"decoding error": {
+			data:    "asdf",
+			wantErr: true,
+		},
+	}
+
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			assert := assert.New(t)
+
+			_, err := parseCRD([]byte(tc.data))
+			if tc.wantErr {
+				assert.Error(err)
+				return
+			}
+			assert.NoError(err)
+		})
+	}
+}