Add rate limiting for import

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

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

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

Start by locating the configuration handling and the import and authentication entry points in the repository, then check how existing options are documented and tested. Clarify whether the requested change is rate limiting for import or auth serialization, and consider the work done only when the intended option behavior and its default are covered by tests.

Written by the indexing model from the issue text.