Users are unable to fully delete their own account

[bennothommo]

The plugin currently provides no way for a user to fully delete their own account - the only option currently available is to deactivate the user's account via the Account component, which soft-deletes the user account but keeps it available in the system. The user account is still visible to administrators, and can be re-activated by simply logging in again.

Given the movement towards data privacy and the right to be forgotten that is happening across the world, it feels prudent that we allow people to delete their own accounts permanently if they wish.

This could perhaps be allowed as a setting, or via another action in the Account component.