Refactor auth for better readability

**Feature request**
It would be great to have caching for lib.

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

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

Start by locating the authentication implementation and configuration handling for lib, then inspect how existing options are declared and consumed. Confirm the intended cache scope and invalidation behavior with maintainers. Done means enable_caching defaults to false and tests cover the disabled and enabled paths.

Written by the indexing model from the issue text.