Update auth documentation

**Feature request**
It would be great to have monitoring for validation.

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

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

No file or test is named. Start by locating the authentication validation entry point and existing configuration or monitoring paths; clarify which validation events should be monitored and how they should be exposed. Done means the enable_monitoring option defaults to false, enables the agreed monitoring behavior, and has coverage for both settings.

Written by the indexing model from the issue text.