I have this to-many relationship which contains at least one element:
Appointment <<------>> Invitee
appointment.invitee
Clearly, this a question that not even the most expert Core Data savants can answer.
The workaround is to model the first element as a separate to-one relationship and the rest as an optional to-many relationship based on the same related entity.
Appointment <<------> mainInvitee (Invitee)
<<------>> additionalInvitees (Invitee)