NGINXaaS: add enable cloud logging api to prereqs (#1404)

Author: valyria257

content/nginxaas-google/monitoring/enable-nginx-logs.md

@@ -13,6 +13,7 @@ F5 NGINXaaS for Google (NGINXaaS) supports integrating with Google Cloud service
 
 ## Prerequisites
 
+- Enable the [Cloud Logging API](https://docs.cloud.google.com/logging/docs/api/enable-api).
 - Configure Workload Identity Federation (WIF). See [our documentation on setting up WIF]({{< ref "/nginxaas-google/monitoring/access-management.md#configure-wif" >}}) for exact steps.
 - Grant a project-level role or grant your principal access to the `roles/logging.viewer` role. See [Google's documentation on controlling access to Cloud Logging with IAM](https://cloud.google.com/logging/docs/access-control).