SAP Fiori - PO Tracking app - acessing Fiori app with RFC user at backend

Hi,

Is there any way wherein SAP Fiori End User can access SAP fiori app by having his Login ID in Gateway system only i.e., EndUser wont be having corresponding UserID in backend ECC system.

Here scenario is like this. We have activated PO Tracking fiori application.

EndUser who is a non-employee will be having Login Id in Gateway system and not in ECC. And when he logs into Fiori launchpad he should be

able to see the Purchase Orders which were assigned to him. I tried with rfcuser in RFC destination, but its giving error while accessing the application.

Is there any way, wherein without having login id in ECC, can we show PO's to the User?

Thanks.