UX/UI designed by Philipp Sauberzweig (@PhilippSauberz).
The event editor dialog is now a NavigationView and the participants
details open in a separate page. Group attendees/participants in
AdwPreferencesGroups and bind groups'
ListBox widgets to backing filter models. These are just "views" into a
single GListStore containing all the event attendees.
Part-of: <https://gitlab.gnome.org/GNOME/gnome-calendar/-/merge_requests/671>
Read-only events show a "Done" button instead of the "Save" button.
The "Done" button does the same thing as "Cancel",
so the "Cancel" button is then redundant.
Likewise, it is impossible to delete events from read-only calendars,
as stated by the banner message in that dialog. In that case,
there's no reason to show a big "Delete" button that you can't click on.
Fixes https://gitlab.gnome.org/GNOME/gnome-calendar/-/issues/1168
Zoey Ahmed