Add handling for Serial numbers added to Unleashed invoice after initial creation

Currently when importing invoices from Unleashed, equipment will be created and any serial numbers on the lines will be set on the equipment at creation. If there are no serial numbers set at the time the equipment is created, this will not be updated if the invoice in Unleashed has serial numbers added at a later date.

We could enhance this by adding a check to see if the equipment does not have a serial number in the CRM, but the invoice has been flagged as being updated and there is now a serial number.

The use case for this would be raising pro-forma invoices in Unleashed, as these will be imported prior to any serial numbers being assigned.