Add unit tests for validation

**Feature request**
It would be great to have pagination for handlers.

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

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

Start by locating the handlers and existing validation tests, then inspect how configuration options are defined and tested. Confirm the intended pagination behavior and the default value for enable_pagination before making changes. Done means the option is covered by unit tests and pagination behavior is verified for handlers.

Scritto dal modello di indicizzazione a partire dal testo della issue.