Improve store performance

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

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

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

Locate the store and model configuration entry points, then trace how configuration options are loaded and applied. Clarify which model events should trigger notifications and how they should be delivered; done means the new enable_notifications option defaults to false and the agreed notification behavior is covered by tests.

Written by the indexing model from the issue text.