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/controllers/settings/two_factor_authentications_controller.rb

@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+module Settings
+  class TwoFactorAuthenticationsController < ApplicationController
+    layout 'admin'
+
+    before_action :authenticate_user!
+    before_action :verify_otp_required, only: [:create]
+
+    def show; end
+
+    def create
+      current_user.otp_secret = User.generate_otp_secret(32)
+      current_user.save!
+      redirect_to new_settings_two_factor_authentication_confirmation_path
+    end
+
+    def destroy
+      current_user.otp_required_for_login = false
+      current_user.save!
+      redirect_to settings_two_factor_authentication_path
+    end
+
+    private
+
+    def verify_otp_required
+      redirect_to settings_two_factor_authentication_path if current_user.otp_required_for_login?
+    end
+  end
+end