Perform backup deletion in a durable job.

app/src/main/protowire/JobData.proto

@@ -217,4 +217,16 @@ message InAppPaymentSetupJobData {
 
 message StorageSyncJobData {
   bool localManifestOutOfDate = 1;
+}
+
+message BackupDeleteJobData {
+  enum Stage {
+    UNKNOWN = 0;
+    CANCEL_SUBSCRIBER = 1;
+    DELETE_MESSAGES = 2;
+    DELETE_MEDIA = 3;
+    CLEAR_LOCAL_STATE = 4;
+  }
+
+  repeated Stage completed = 1;
 }