Backup Datastore using the Admin REST API

Add server end points to backup Datastore using managed-export mechanism.
A cron job is defined in Alpha to run daily exports using this implementation.

Existing backup is left running. The new backups are saved to a new set of
locations:
- GCS bucket: gs://PROJECT-ID-datastore-backups
- Big Query data set: datastore_backups
- Big Query latest back up view name: latest_datastore_backup
Also, the names of Bigquery tables now use the export timestamp
assigned by Datastore. E.g., 2018_12_05T23_56_18_50532_ContactResource,

After the new import mechanism is implemented and the back-restore flow is
tested, we will stop the existing backup runs and deploy the new
implementation to all environments.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=224932957

java/google/registry/module/backend/BackendRequestComponent.java

@@ -39,7 +39,9 @@ import google.registry.dns.writer.VoidDnsWriterModule;
 import google.registry.dns.writer.clouddns.CloudDnsWriterModule;
 import google.registry.dns.writer.dnsupdate.DnsUpdateConfigModule;
 import google.registry.dns.writer.dnsupdate.DnsUpdateWriterModule;
+import google.registry.export.BackupDatastoreAction;
 import google.registry.export.BigqueryPollJobAction;
+import google.registry.export.CheckBackupAction;
 import google.registry.export.CheckSnapshotAction;
 import google.registry.export.ExportDomainListsAction;
 import google.registry.export.ExportPremiumTermsAction;
@@ -49,6 +51,7 @@ import google.registry.export.ExportSnapshotAction;
 import google.registry.export.LoadSnapshotAction;
 import google.registry.export.SyncGroupMembersAction;
 import google.registry.export.UpdateSnapshotViewAction;
+import google.registry.export.UploadDatastoreBackupAction;
 import google.registry.export.sheet.SheetModule;
 import google.registry.export.sheet.SyncRegistrarsSheetAction;
 import google.registry.flows.async.AsyncFlowsModule;
@@ -114,8 +117,10 @@ import google.registry.tmch.TmchSmdrlAction;
         WhiteboxModule.class,
     })
 interface BackendRequestComponent {
+  BackupDatastoreAction backupDatastoreAction();
   BigqueryPollJobAction bigqueryPollJobAction();
   BrdaCopyAction brdaCopyAction();
+  CheckBackupAction checkBackupAction();
   CheckSnapshotAction checkSnapshotAction();
   CommitLogCheckpointAction commitLogCheckpointAction();
   CommitLogFanoutAction commitLogFanoutAction();
@@ -158,6 +163,7 @@ interface BackendRequestComponent {
   TmchCrlAction tmchCrlAction();
   TmchDnlAction tmchDnlAction();
   TmchSmdrlAction tmchSmdrlAction();
+  UploadDatastoreBackupAction uploadDatastoreBackupAction();
   UpdateSnapshotViewAction updateSnapshotViewAction();
   PublishInvoicesAction uploadInvoicesAction();