Add moderator role and add pundit policies for admin actions (#5635)

* Add moderator role and add pundit policies for admin actions

* Add rake task for turning user into mod and revoking it again

* Fix handling of unauthorized exception

* Deliver new report e-mails to staff, not just admins

* Add promote/demote to admin UI, hide some actions conditionally

* Fix unused i18n

app/controllers/admin/two_factor_authentications_controller.rb

@@ -5,6 +5,7 @@ module Admin
     before_action :set_user
 
     def destroy
+      authorize @user, :disable_2fa?
       @user.disable_two_factor!
       redirect_to admin_accounts_path
     end