Status if this appointment represents an invitation
public enum InvitationStatus
2: 2: The invitation has been accepted
10: 10: The meeting has been cancelled.
9: 9: The invitation has been declined/rejected
4: 4: Hidden
5: 5: An invitation to a meeting not observed by the attending party
6: 6: The meeting has been moved
8: 8: The meeting has been moved, and this is observed by the attending party
1: 1: Default value when the appointment is not a booking child
7: 7: An invitation to a meeting observed by the attending party. This can also be viewed upon as a tentative response to participate in the meeting.
0: Unknown - used when initializing