2FA controller cleanup (#2296)

* 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

config/routes.rb

@@ -58,11 +58,10 @@ Rails.application.routes.draw do
       resources :mutes, only: :index, controller: :muted_accounts
     end
 
-    resource :two_factor_auth, only: [:show, :new, :create] do
-      member do
-        post :disable
-        post :recovery_codes
-      end
+    resource :two_factor_authentication, only: [:show, :create, :destroy]
+    namespace :two_factor_authentication do
+      resources :recovery_codes, only: [:create]
+      resource :confirmation, only: [:new, :create]
     end
   end