Optimize auth for large datasets

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

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

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

No files or tests are named. Start by locating the store implementation and configuration entry point, then define the serialized format and cover both the default-disabled and enabled cases; done means serialization works for large stores without changing default behavior.

Written by the indexing model from the issue text.