Request becoming an admin


I would like to develop a feature which let’s anyone signup as an admin (of course without having any access to the CMS until confirmed by another admin, or super-admin). I can’t find any information if this kind of approach is even doable.

I am aware there is a controller for signing up as an end user, but is the same possible for admins? Or is it set in stone that they have to be invited to the service by another admin?

Thanks in advance!