Update handlers documentation

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

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

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

No files, tests, or entry points are named. Start by locating the handlers configuration and validation paths, then check how existing options are documented and tested. Done means a documented `enable_analytics` option defaults to `false` and validation analytics work as described for production deployments.

Written by the indexing model from the issue text.