Define `Settings::BaseController#set_body_classes` so that sub classes
inherit `Settings::BaseController` don't need to define
`#set_body_classes` agein.
* Fix#3910 - Require OTP authentication to disable 2FA. Also, remove ability
to generate new OTP backup codes *after* initial backup codes were handed
out during activation
* Restore recovery code re-generation
* Improve display of some 2FA elements
* Add spec coverage for settings/two_factor_auth area
* extract setup method for qr code
* Move otp required check to before action
* Merge method only used once
* Remove duplicate view
* Consolidate creation of @codes for backup
* Move settings/2fq#recovery_codes to settings/recovery_codes#create
* Rename settings/two_factor_auth#disable to #destroy
* Add coverage for the otp required path on 2fa#show
* Clean up the recovery codes list styles
* Move settings/two_factor_auth to settings/two_factor_authentication
* Reorganize the settings two factor auth area
Updated to use a flow like:
- settings/two_factor_authentication goes to a #show view which has a button
either enable or disable 2fa on the account
- the disable button turns off the otp requirement for the user
- the enable button cycles the user secret and redirects to a confirmation page
- the confirmation page is a #new view which shows the QR code for user
- that page posts to #create which verifies the code, and creates the recovery
codes
- that create action shares a view with a recovery codes controller which can be
used separately to reset codes if needed
