added prepare_backup_projects_for_terraform.sh and update README

README.md

@@ -415,7 +415,9 @@ BigQuery Types to Avro Logical Types mapping:
 | `TIME`     | `timestamp-micro` (annotates Avro `LONG`)       | 
 | `DATETIME` | `STRING` (custom named logical type `datetime`) | 
 
-##### Configure Additional Backup Projects
+##### Configure Backup Projects
+
+###### Additional Backup Projects
 
 Terraform needs to deploy resources to the backup projects where the backup operations will run. For example, log
 sinks that send notifications to the Tagger once a backup operation has completed.
@@ -430,6 +432,18 @@ additional_backup_projects = ["project1", "project2", ..]
 
 If you're only using the fallback backup policy and without table-level external policies, you can set this variable to an empty list `[]`
 
+###### Configure Terraform SA permissions on Backup Projects
+
+In order for Terraform to deploy resources on the backup projects (configured in the previous step), the service account
+used by Terraform must have the required permissions on these projects. To do so, run the following command:
+
+```shell
+./scripts/prepare_backup_projects_for_terraform.sh <project1> <project2> <etc>
+```
+
+The list of projects must include all projects you're planning to store backups in. This includes all projects listed under the `backup_project` 
+field in the fallback policy, plus the ones included in the `additional_backup_projects` Terraform variable. 
+
 #### Terraform Deployment
 
 ```shell
@@ -446,7 +460,6 @@ terraform apply -var-file=$VARS -auto-approve
 
 ```
 
-
 #### Setup Access to Sources and Destinations
 
 ##### Set Environment Variables

scripts/prepare_backup_projects_for_terraform.sh

@@ -0,0 +1,32 @@
+#!/bin/bash
+
+#
+# Copyright 2022 Google LLC
+#
+# 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
+#
+#     https://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.
+#
+
+# run this script for all projects that are used to store backups
+set -e
+
+for project in "$@"
+do
+
+  echo "Preparing backup project ${project} for Terraform .."
+
+   # Terraform needs to create log sinks to capture GCS export operation completion
+  gcloud projects add-iam-policy-binding "${project}" \
+      --member="serviceAccount:${TF_SA}@${PROJECT_ID}.iam.gserviceaccount.com" \
+      --role="roles/logging.configWriter"
+
+done