Add unit tests for auth

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

**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 authentication configuration and existing unit-test conventions in the repository. Clarify how import validation should work and where `enable_import` belongs before implementing it. Done means the option defaults to `false` and tests cover the intended validation behavior.

Written by the indexing model from the issue text.