feat(sales): currency code associated from invoice customer.

feat(purchases): currency code associated from vendor customer.

server/src/database/migrations/20200715193633_create_sale_invoices_table.js

@@ -13,6 +13,7 @@ exports.up = function(knex) {
 
     table.decimal('balance', 13, 3);
     table.decimal('payment_amount', 13, 3);
+    table.string('currency_code', 3);
 
     table.string('inv_lot_number').index();