Fix method overlap for issue sorting

app/models/concerns/internal_id.rb

 module InternalId
   extend ActiveSupport::Concern
-  include Sortable
 
   included do
     validate :set_iid, on: :create

app/models/concerns/sortable.rb

@@ -17,7 +17,7 @@ module Sortable
   end
 
   module ClassMethods
-    def sort(method)
+    def order_by(method)
       case method.to_s
       when 'name' then order_name_asc
       when 'recent' then order_recent
@@ -25,7 +25,7 @@ module Sortable
       when 'recent_updated' then order_recent_updated
       when 'oldest_updated' then order_oldest_updated
       else
-        self
+        all
       end
     end
   end

app/models/issue.rb

@@ -24,6 +24,7 @@ class Issue < ActiveRecord::Base
   include Issuable
   include InternalId
   include Taskable
+  include Sortable
 
   ActsAsTaggableOn.strict_case_match = true
 

app/models/merge_request.rb

@@ -28,6 +28,7 @@ class MergeRequest < ActiveRecord::Base
   include Issuable
   include Taskable
   include InternalId
+  include Sortable
 
   belongs_to :target_project, foreign_key: :target_project_id, class_name: "Project"
   belongs_to :source_project, foreign_key: :source_project_id, class_name: "Project"

app/models/milestone.rb

@@ -15,6 +15,7 @@
 
 class Milestone < ActiveRecord::Base
   include InternalId
+  include Sortable
 
   belongs_to :project
   has_many :issues