change transactional primary key to custom ID for better portability

db/migrate/20170403163734_create_sale_payments.rb

@@ -1,13 +1,15 @@
 class CreateSalePayments < ActiveRecord::Migration[5.0]
   def change
-    create_table :sale_payments do |t|
-      t.references :sale, foreign_key: true
+    create_table :sale_payments, :id => false, :primary_key => :sale_payment_id do |t|
+      t.string :sale_payment_id, :limit => 16, :null => false, :index => true, :unique => true #custom primary key - to ensure consistence for cloud syncing
+
+      t.string :sale_id, foreign_key: true, :limit => 16
       t.string :payment_method, :null => false, :default => "cash"
       t.decimal :payment_amount, :precision => 10, :scale => 2, :null => false, :default => 0.00
       t.decimal :outstanding_amount, :precision => 10, :scale => 2, :null => false, :default => 0.00
       t.string :payment_reference
       t.string :payment_status, :null => false, :default => "new"
-      
+
       t.timestamps
     end
   end