Add TypeScript types for controllers

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

**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 reconciling the title's TypeScript controller request with the body’s route notifications and `enable_notifications` option; confirm the intended scope and acceptance criteria before locating the relevant code. Done is undefined until that mismatch is resolved.

Written by the indexing model from the issue text.