Add rate limiting for search

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

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

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

The title asks for search rate limiting, while the body requests API notifications and an `enable_notifications` option defaulting to `false`. Start by locating the configuration handling and API notification entry points; the scope must be clarified before implementation, and done should include the agreed behavior and coverage for the new option.

Written by the indexing model from the issue text.