Add unit tests for services

**Feature request**
It would be great to have encryption for models.

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

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

Start by reviewing the service and configuration entry points; the issue names no files or tests. Clarify how model encryption should work and where the `enable_encryption` option belongs before defining the required unit tests. Done means the option defaults to `false`, encryption behavior is specified, and the relevant service tests pass.

Written by the indexing model from the issue text.