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/locales/zh-HK.yml

@@ -276,7 +276,7 @@ zh-HK:
     import: 匯入
     preferences: 偏好設定
     settings: 設定
-    two_factor_auth: 雙重認證
+    two_factor_authentication: 雙重認證
   statuses:
     open_in_web: 開啟網頁
     over_character_limit: 超過了 %{max} 字的限制
@@ -292,7 +292,7 @@ zh-HK:
   time:
     formats:
       default: "%Y年%-m月%d日 %H:%M"
-  two_factor_auth:
+  two_factor_authentication:
     code_hint: 請輸入你認證器產生的代碼，以確認設定
     description_html: 當你啟用<strong>雙重認證</strong>後，你登入時將需要使你手機、或其他種類認證器產生的代碼。
     disable: 停用