<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Api/etc/extension_attributes.xsd">
    <extension_attributes for="Magento\Sales\Api\Data\OrderInterface">
        <attribute code="erp_sales_order" type="DJOGlobal\ErpOrderSync\Api\Data\ErpSalesOrderInterface"/>
    </extension_attributes>
    <extension_attributes for="Magento\Sales\Api\Data\OrderItemInterface">
        <attribute code="erp_sales_order_item" type="DJOGlobal\ErpOrderSync\Api\Data\ErpSalesOrderItemInterface"/>
    </extension_attributes>
</config>
