add instance code to assigned_order_items

db/migrate/20170414090001_create_assigned_order_items.rb

@@ -3,6 +3,7 @@ class CreateAssignedOrderItems < ActiveRecord::Migration[5.1]
     create_table :assigned_order_items, :id => false do |t|
       t.string :assigned_order_item_id, :limit => 16, :primary_key => true #custom primary key - to ensure consistence for cloud syncing
       t.string     :item_code, :null => false, :index => true
+      t.string :instance_code, :null => false, :index => true
       t.references :order_queue_station, foreign_key: true
       t.string :order_id, foreign_key: true, :limit => 16
       t.boolean :print_status