* jane creates a recurrenting event with john as attendee
* john sees the recurrenting event in his calendar and creates a exception for the one occurence (right client ->"diassosiate from recurrence")
(must we send here a mail?)
* john sees the exception and can edit it idependently
* john decline the exception
* mail is send to jane with his decline
*john sees for all other occurence the event in invitation folder