Consider deprecating old api API

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

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

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

No file or entry point is named. Start by locating hook handling and configuration parsing, then determine how notifications should be connected and where the `enable_notifications` default belongs. Done means the option defaults to false and hook notifications work when it is enabled, with tests covering both settings.

Written by the indexing model from the issue text.