Since fields like sourceIdentifier, reportEndpoint etc. will be specific to the Ad and will likely be embedded within the body of the ad, some mechanism is needed to parse this data out from the ad and help populate the UIEventAttribution data structure.
Closing this ticket for now. Need to discuss with internal iOS team first before filing the ticket here.
Confirmed with internal iOS team. This ticket is good to go from our side and we are happy to answer any question from the WebKit team