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

javatests/google/registry/export/BackupDatastoreActionTest.java

@@ -0,0 +1,85 @@
+// Copyright 2018 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package google.registry.export;
+
+import static com.google.common.truth.Truth.assertThat;
+import static google.registry.export.CheckBackupAction.CHECK_BACKUP_KINDS_TO_LOAD_PARAM;
+import static google.registry.export.CheckBackupAction.CHECK_BACKUP_NAME_PARAM;
+import static google.registry.testing.TaskQueueHelper.assertTasksEnqueued;
+import static org.mockito.Mockito.when;
+
+import com.google.common.base.Joiner;
+import google.registry.export.datastore.DatastoreAdmin;
+import google.registry.export.datastore.DatastoreAdmin.Export;
+import google.registry.export.datastore.Operation;
+import google.registry.testing.AppEngineRule;
+import google.registry.testing.FakeResponse;
+import google.registry.testing.MockitoJUnitRule;
+import google.registry.testing.TaskQueueHelper.TaskMatcher;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+import org.mockito.Mock;
+
+/** Unit tests for {@link BackupDatastoreAction}. */
+@RunWith(JUnit4.class)
+public class BackupDatastoreActionTest {
+
+  @Rule public final AppEngineRule appEngine = AppEngineRule.builder().withTaskQueue().build();
+  @Rule public final MockitoJUnitRule mocks = MockitoJUnitRule.create();
+
+  @Mock private DatastoreAdmin datastoreAdmin;
+  @Mock private Export exportRequest;
+  @Mock private Operation backupOperation;
+
+  private final FakeResponse response = new FakeResponse();
+  private final BackupDatastoreAction action = new BackupDatastoreAction();
+
+  @Before
+  public void before() throws Exception {
+    action.datastoreAdmin = datastoreAdmin;
+    action.response = response;
+
+    when(datastoreAdmin.export(
+            "gs://registry-project-id-datastore-backups", ExportConstants.getBackupKinds()))
+        .thenReturn(exportRequest);
+    when(exportRequest.execute()).thenReturn(backupOperation);
+    when(backupOperation.getName())
+        .thenReturn("projects/registry-project-id/operations/ASA1ODYwNjc");
+    when(backupOperation.getExportFolderUrl())
+        .thenReturn("gs://registry-project-id-datastore-backups/some-id");
+  }
+
+  @Test
+  public void testBackup_enqueuesPollTask() {
+    action.run();
+    assertTasksEnqueued(
+        CheckBackupAction.QUEUE,
+        new TaskMatcher()
+            .url(CheckBackupAction.PATH)
+            .param(CHECK_BACKUP_NAME_PARAM, "projects/registry-project-id/operations/ASA1ODYwNjc")
+            .param(
+                CHECK_BACKUP_KINDS_TO_LOAD_PARAM,
+                Joiner.on(",").join(ExportConstants.getReportingKinds()))
+            .method("POST"));
+    assertThat(response.getPayload())
+        .isEqualTo(
+            "Datastore backup started with name: "
+                + "projects/registry-project-id/operations/ASA1ODYwNjc\n"
+                + "Saving to gs://registry-project-id-datastore-backups/some-id");
+  }
+}