Add rate limiting for caching

**Feature request**
It would be great to have notifications for types.

**Use case**
Many users need this functionality for production deployments.

**Implementation idea**
Add a new config option `enable_notifications` with default `false`.

First reconcile the title, which asks for caching rate limiting, with the body, which requests notifications and the enable_notifications option. Locate the configuration entry point and notification-related code, then determine the intended behavior and tests before making changes. Done should match the confirmed request and preserve a default of false if notifications are the scope.

Written by the indexing model from the issue text.