Improve error messages in handlers

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

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

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

Start by locating the handlers and configuration entry points related to auth and imports. Confirm how configuration defaults are loaded, then add the enable_import option with false as its default and verify that import behavior remains disabled by default and works when enabled.

Written by the indexing model from the issue text.