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

app/views/settings/two_factor_authentication/confirmations/new.html.haml

@@ -0,0 +1,17 @@
+- content_for :page_title do
+  = t('settings.two_factor_authentication')
+
+= simple_form_for @confirmation, url: settings_two_factor_authentication_confirmation_path, method: :post do |f|
+  %p.hint= t('two_factor_authentication.instructions_html')
+
+  .qr-wrapper
+    .qr-code= raw @qrcode.as_svg(padding: 0, module_size: 4)
+
+    .qr-alternative
+      %p.hint= t('two_factor_authentication.manual_instructions')
+      %samp.qr-alternative__code= current_user.otp_secret.scan(/.{4}/).join(' ')
+
+  = f.input :code, hint: t('two_factor_authentication.code_hint'), placeholder: t('simple_form.labels.defaults.otp_attempt')
+
+  .actions
+    = f.button :button, t('two_factor_authentication.enable'), type: :submit

app/views/settings/two_factor_authentication/recovery_codes/index.html.haml

@@ -0,0 +1,9 @@
+- content_for :page_title do
+  = t('settings.two_factor_authentication')
+
+%p.hint= t('two_factor_authentication.recovery_instructions')
+
+%ol.recovery-codes
+  - @recovery_codes.each do |code|
+    %li<
+      %samp= code