Support backup configuration

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

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

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

No files, tests, or entry points are identified. First locate the configuration entry point and authentication path, then clarify the intended caching behavior for production deployments. Done should be defined by an agreed default-false enable_caching option and tests covering the resulting auth behavior.

Written by the indexing model from the issue text.