Fix merge conflict

lib/two_factor_authentication.rb

@@ -30,6 +30,9 @@ module Devise
 
   mattr_accessor :second_factor_resource_id
   @@second_factor_resource_id = 'id'
+
+  mattr_accessor :delete_cookie_on_logout
+  @@delete_cookie_on_logout = false
 end
 
 module TwoFactorAuthentication

lib/two_factor_authentication/hooks/two_factor_authenticatable.rb

@@ -11,3 +11,7 @@ Warden::Manager.after_authentication do |user, auth, options|
     end
   end
 end
+
+Warden::Manager.before_logout do |user, auth, _options|
+  auth.cookies.delete TwoFactorAuthentication::REMEMBER_TFA_COOKIE_NAME if user.class.delete_cookie_on_logout
+end

lib/two_factor_authentication/models/two_factor_authenticatable.rb

@@ -16,7 +16,8 @@ module Devise
         ::Devise::Models.config(
           self, :max_login_attempts, :allowed_otp_drift_seconds, :otp_length,
           :remember_otp_session_for_seconds, :otp_secret_encryption_key,
-          :direct_otp_length, :direct_otp_valid_for, :totp_timestamp)
+          :direct_otp_length, :direct_otp_valid_for, :totp_timestamp, :delete_cookie_on_logout
+        )
       end
 
       module InstanceMethodsOnActivation