website/admin: make it possible for users to change their own active status

[icxes]

if someone knows they're not going to be active they ought to be able change this without asking an admin

[Wessie]

Which active status are we talking about here?

[icxes]

I'm... actually not sure anymore, either schedule or staff page.

If this was related to the schedule, then currently the DJ for a particular day in the schedule is set on the admin schedule page and presumably requires admin/dev permissions, but a DJ should be able to change whether they're shown on the schedule page or not by themselves.

Alternatively I might've been thinking that DJs should be able to toggle their own visibility on the staff page, which I think only dev/admin can do now. People who aren't visible on staff page shouldn't be shown on the schedule page either, I guess.