I've pulled down all purchase invoices and purchase orders via the standard api's (endpoints purchaseOrders and purchaseInvoices), I used the ?$expand = purchaseOrderLines/purchaseInvoiceLines in order to get the respective lines. Is there a field that joins these two datasets? I can join on vendor,postingDate,itemNumber and variantCode but I'm left with some duplicates. I could identify these and weed them out with some SQL code, however I would suspect that there is a field in BC somewhere that allows me to join these two sets?