In SOAP api there was a possibility to delete empty packages and releases. We cannot replicate the exact same API with REST as the approach is not RESTful but we can provide the following en points
GET /projects/:id/frs_packages?query={"is_empty": true}
The result is paginated
GET /frs_packages/:id/frs_releases?query={"is_empty": true}
The result is paginated
DELETE /frs_releases/:id
It can only delete releases that doesn't have any files in it.
DELETE /frs_packages/:id
It can only delete packages that doesn't have any releases in it