https://userapps.support.sap.com/sap/support/knowledge/en/3009083
3009083 - Extend FDP_EF_PURCHASE_ORDER_SRV with custom fields to appear on MM_PUR_PURCHASE_ORDER...
The service FDP_EF_PURCHASE_ORDER_SRV is expected to extend with some custom logic (for example custom fields) to influence the S4hana Gateway service relevant...