Update config documentation

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

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

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

The payload names no file or test; start by locating configuration parsing and the hook handling entry point. Add the documented enable_backup option with a false default, then verify that enabling it provides hook backups and that the default preserves current behavior.

Written by the indexing model from the issue text.