Add configuration options for filtering

**Feature request**
It would be great to have search for auth.

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

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

No files or tests are named. Start by locating the configuration handling and the authentication search entry point, then trace how search behavior is selected. Done means a documented enable_search option defaults to false and authentication search is available when it is enabled, with relevant tests passing.

Written by the indexing model from the issue text.