Refactor `TokenAuthenticatable` to improve reusability

app/models/application_setting.rb

@@ -31,6 +31,9 @@
 #
 
 class ApplicationSetting < ActiveRecord::Base
+  include TokenAuthenticatable
+  add_authentication_token_field :runners_registration_token
+
   CACHE_KEY = 'application_setting.last'
 
   serialize :restricted_visibility_levels

app/models/concerns/token_authenticatable.rb

 module TokenAuthenticatable
   extend ActiveSupport::Concern
 
-  module ClassMethods
-    def find_by_authentication_token(authentication_token = nil)
-      if authentication_token
-        where(authentication_token: authentication_token).first
-      end
+  class_methods do
+    def authentication_token_fields
+      @token_fields || []
     end
-  end
 
-  def ensure_authentication_token
-    if authentication_token.blank?
-      self.authentication_token = generate_authentication_token
-    end
-  end
+    private
+
+    def add_authentication_token_field(token_field)
+      @token_fields = [] unless @token_fields
+      @token_fields << token_field
 
-  def reset_authentication_token!
-    self.authentication_token = generate_authentication_token
-    save
+      define_singleton_method("find_by_#{token_field}") do |token|
+        where(token_field => token).first if token
+      end
+
+      define_method("ensure_#{token_field}") do
+        write_attribute(token_field, generate_token_for(token_field)) if
+          read_attribute(token_field).blank?
+      end
+
+      define_method("reset_#{token_field}!") do
+        write_attribute(token_field, generate_token_for(token_field))
+        save
+      end
+    end
   end
 
   private
 
-  def generate_authentication_token
+  def generate_token_for(token_field)
     loop do
       token = Devise.friendly_token
-      break token unless self.class.unscoped.where(authentication_token: token).first
+      break token unless self.class.unscoped.where(token_field => token).first
     end
   end
 end

app/models/user.rb

@@ -69,8 +69,10 @@ class User < ActiveRecord::Base
   include Gitlab::CurrentSettings
   include Referable
   include Sortable
-  include TokenAuthenticatable
   include CaseSensitivity
+  include TokenAuthenticatable
+
+  add_authentication_token_field :authentication_token
 
   default_value_for :admin, false
   default_value_for :can_create_group, gitlab_config.default_can_create_group