Switch backup finalizer to DeleteBackupRequest

We ran into a lot of problems using a finalizer on the backup to allow
the Ark server to clean up all associated backup data when deleting a
backup.

Users also found it less than desirable that deleting the heptio-ark
namespace resulted in all the backup data being deleted.

This removes the finalizer and replaces it with an explicit
DeleteBackupRequest that is created as a means of requesting the
deletion of a backup and all its associated data. This is what `ark
backup delete` does.

If you use kubectl to delete a backup or to delete the heptio-ark
namespace, this no longer deletes associated backups. Additionally, as
long as the heptio-ark namespace still exists, the Ark server's
BackupSyncController will continually sync backups into the heptio-ark
namespace from object storage.

Signed-off-by: Andy Goldstein <andy.goldstein@gmail.com>

pkg/controller/backup_controller.go

@@ -49,7 +49,6 @@ import (
 	"github.com/heptio/ark/pkg/util/collections"
 	"github.com/heptio/ark/pkg/util/encode"
 	kubeutil "github.com/heptio/ark/pkg/util/kube"
-	"github.com/heptio/ark/pkg/util/stringslice"
 )
 
 const backupVersion = 1
@@ -237,11 +236,6 @@ func (controller *backupController) processBackup(key string) error {
 	// set backup version
 	backup.Status.Version = backupVersion
 
-	// add GC finalizer if it's not there already
-	if !stringslice.Has(backup.Finalizers, api.GCFinalizer) {
-		backup.Finalizers = append(backup.Finalizers, api.GCFinalizer)
-	}
-
 	// calculate expiration
 	if backup.Spec.TTL.Duration > 0 {
 		backup.Status.Expiration = metav1.NewTime(controller.clock.Now().Add(backup.Spec.TTL.Duration))