Improve controllers performance

**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`.

Start by locating the controller and handler entry points, then inspect how configuration options are defined and how existing handler events are reported. Confirm the expected notification behavior with the issue discussion; done means an `enable_notifications` option defaults to `false` and notifications are emitted when enabled.

Written by the indexing model from the issue text.