Implement retain function in MB reconciler

It should be also implemented in MB reconciler as well as expiration.

Signed-off-by: Toshikuni Fukaya <toshikuni-fukaya@cybozu.co.jp>

internal/controller/mantlebackup_controller.go

@@ -35,6 +35,7 @@ const (
 	labelLocalBackupTargetPVCUID  = "mantle.cybozu.io/local-backup-target-pvc-uid"
 	labelRemoteBackupTargetPVCUID = "mantle.cybozu.io/remote-backup-target-pvc-uid"
 	annotRemoteUID                = "mantle.cybozu.io/remote-uid"
+	annotRetainIfExpired          = "mantle.cybozu.io/retain-if-expired"
 )
 
 // MantleBackupReconciler reconciles a MantleBackup object
@@ -267,6 +268,12 @@ func (r *MantleBackupReconciler) expire(ctx context.Context, backup *mantlev1.Ma
 		return nil
 	}
 
+	if v, ok := backup.Annotations[annotRetainIfExpired]; ok && v == "true" {
+		// retain this backup.
+		// If the annotation is deleted, reconciliation will run, so no need to schedule.
+		return nil
+	}
+
 	expire, err := strfmt.ParseDuration(backup.Spec.Expire)
 	if err != nil {
 		return err