App Engine is changing the URLs that you use to send requests to your apps

## Change App Engine is changing the URLs that you use to send requests to your apps. URLs now [include a region ID](https://cloud.google.com/appengine/docs/standard/python/how-requests-are-routed#region-id) to help Google route your requests more efficiently and reliably. For example, an app can receive requests at `https://PROJECT_ID.REGION_ID.r.appspot.com`. This new URL is optional for existing apps and is provided for all new apps. To ensure a smooth transition, we are slowly updating App Engine to use region IDs. If we haven't updated your Google Cloud project yet, you won't see a region ID for your app. Since the ID is optional for existing apps, you don't need to update URLs or make other changes once the region ID is available for your existing apps.