Stalwart 1.0 enforces maxParticipantsPerEvent (20 by default) on every
CalendarEvent create and update, answers to invitations included, and
refuses anything over it with invalidProperties "An event cannot have
more than 20 participants.". 0.16 advertises the same value but never
enforced it. Creating, editing, moving or answering a bigger meeting
failed with a generic "Failed to save event".
- read the limit from the calendars account capability and warn in the
event editor when the attendees go over it, without blocking the save
- name the limit, and that an administrator can raise it, when the
server refuses a create, edit, move, resize or answer for it, in the
calendar and in the invitation banner
- keep the SetError type on refused event creates and updates
Linus Rath
81b196a6ca