Issue:
For some call-out notifications the actual trigger (sub) event is not available as event parameter that can be included in the notification message. Example: the "Invoice Posted" event has three trigger events: Manual, API, and BillRun. However this event type is not available as event parameter and the only way to pass the even trigger type would be using a URL based parameter: http://...../service?Eventrigger=API. This a cumberstone solution.
Proposal:
Always make the trigger (sub) event available as an event parameter even if that information is available on a entity/datasource field ). For instance as "Event.EventTrigger" parameter
