Remove temporary files from DB

Students can have files uploaded that are not removed from the DB, for instance, if the application remains on draft or either if they are not part of the final version of the submitted application. We should ensure that temporary uploaded files are removed from the DB from time to time.

- [ ] Define the criteria to purge files from DB (potentially creating a scheduler).
- [ ] Check if there is an appetite to invest time looking into an alternative approach to store files, for instance, using the BC Gov shared services like https://digital.gov.bc.ca/bcgov-common-components/common-object-management-service.