Optimize controllers for large datasets

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

**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 middleware implementation and configuration entry points for the Operator agent. Trace how middleware currently runs, then determine how the `enable_notifications` option should control notifications and define a testable production behavior; the issue does not name specific files or tests.

Written by the indexing model from the issue text.