Optimize models for large datasets

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

**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. Start by locating controller handling, configuration parsing, and any existing notification code, then clarify how notifications should behave in production deployments. Done should include the enable_notifications option defaulting to false and a defined, tested notification behavior.

Written by the indexing model from the issue text.