Allow admins to delete user accounts (#38)

* Add permission function

* Update permission function

* format with prettier

* Add deleteAccount function

* move userId from body into api param

* change api path

* Generate more users in db seeder

---------

Co-authored-by: neda_moshki <uzijb@student.kit.edu>
Co-authored-by: Florian Raith <florianraith00@gmail.com>