To link to POL:
1. Try to match on POL. If single match, link the invoice line. If no or multiple matches, go to 2.
2. Try to match on any Vendor Ref Number (ignore vendor ref number type?). If any 1 number matches a Vendor Ref number on a POL as a single match, link the invoice line. If no or multiple matches, load the invoice line as unlinked (can we flag as no match versus multiple matches?)