single method for updating cart item state / fixed problems with sinatra contrib

front-api/models/cart.rb

@@ -1,6 +1,5 @@
 class Cart < ActiveRecord::Base
-  has_many :item_in_carts
-
+  has_many :item_in_carts, -> { order "created_at" }
   def self.find_or_create(anonymous_id, user_id)
     cart = Cart.where(user_id: user_id).where(ordered: false).first
     cart ||= Cart.where(anonymous_id_string: anonymous_id).where(ordered: false).first