Add rate limiting for retry

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

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

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

No files, tests, or entry points are named. First clarify the mismatch between the title's retry rate limiting and the body’s handler notifications, then locate the configuration and handler paths; done should include a defined notification behavior and the new enable_notifications option defaulting to false.

Written by the indexing model from the issue text.