add labels for notebook so that gcp credentials will be injected by webhook (kubeflow/kubeflow#2853)

* add labels for gcp cred

* kfctl set flag

* review comment

* review comment

components/notebook-controller/pkg/controller/notebook/notebook_controller.go

@@ -18,6 +18,7 @@ package notebook
 
 import (
 	"context"
+	"os"
 	"strings"
 
 	v1alpha1 "github.com/kubeflow/kubeflow/components/notebook-controller/pkg/apis/notebook/v1alpha1"
@@ -283,6 +284,24 @@ func generateStatefulSet(instance *v1alpha1.Notebook) *appsv1.StatefulSet {
 			},
 		},
 	}
+
+	// Inject GCP credentials
+	if labels := os.Getenv("POD_LABELS"); labels != "" {
+		// labels should be comma separated labels, e.g. "k1=v1,k2=v2"
+		l := &ss.Spec.Template.ObjectMeta.Labels
+		labelList := strings.Split(labels, ",")
+		for _, label := range labelList {
+			// label is something like k1=v1
+			s := strings.Split(label, "=")
+			if len(s) != 2 {
+				log.Info("Invalid env var POD_LABELS, skip..")
+				continue
+			}
+			// s[0] = k1, s[1] = v1
+			(*l)[s[0]] = s[1]
+		}
+	}
+
 	podSpec := &ss.Spec.Template.Spec
 	container := &podSpec.Containers[0]
 	if container.WorkingDir == "" {