title: Acumatica - Import Scenario - Find customer using custom field
body: <p>I'm building an import scenario so CSV's from an external system can be imported into Sales Orders.</p>
  
  <p>The external system has a list of customers, with their own ids.
  Acumatica also has a list of customers, and a custom field that stores the external systems customer id.</p>
  
  <p>Is it possible to configure the import scenario to designate the customer by matching by this custom field?</p>
  
  <p>i.e. Say on the Order Summary target object, rather than setting the Customer -> Customer ID, can I use Customer -> Ext. Customer ID</p>