Add ability to add multiple purchase orders per workorder

Currently, when we open a repair order for a purchase order received, we can not add to that existing repair order if another purchase order comes in. The PO will not allow us to add to a open RO that has a PO already associated with it. Can this be changed so we can add to a open repair order with one or more PO.

This will allow us to clearly assign work from our sale team, and eliminate approx. 700-1000 repairs orders opened. This will allow all users to correctly and accurately track open repairs orders vs. vehicles repairs/serviced