Add unit tests for core

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

**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 core configuration handling and the existing unit tests referenced by the title. Trace how configuration options are defined and consumed, then verify that enable_import defaults to false and that the requested config import behavior is covered by tests.

Written by the indexing model from the issue text.