added menu sub sub items (horrible name i know)

front-api/models/menu_sub_item.rb

@@ -1,3 +1,4 @@
 class MenuSubItem < ActiveRecord::Base
     belongs_to :menu_item
+    has_many :menu_sub_sub_items
 end

front-api/models/menu_sub_sub_item.rb

@@ -0,0 +1,3 @@
+class MenuSubSubItem < ActiveRecord::Base
+    belongs_to :menu_sub_item
+end