How to add attendees to a calendar event in iOS?

I've been searching an answer to this question for quite some time. I read a previous question that was asked about two years ago, but didn't find any answer (Add participant to an event in iOS).

So I will ask it again, as it is critical for our product and we haven't been able to find a way yet: How can you programmatically add invitees to a calendar event in iOS.

I know that the attendees property is read-only and the ways that these EKParticipant's come into existence is omitted from the reference. But I also know that some apps are able to do it... so there must be a way.

Does anybody know the answer to this strange puzzle ?

Thanks a lot for your time and consideration ! Ingrid.