I just configured CalDAV calendar which I normally use via Thunderbird for
read/write purposes via CalDAV protocol. Everything goes well except that I am
unable to edit that calendar as I always get: "Event cannot be edited, because
selected calendar is read only". 
Problem is that I cant see option how to toggle it from read-only to read-write
or vice-versa. On "Calendar" view in Evolution I see "cable discconected" icon
on this calendar.
I found several reports through google on different distros, but I am unsure if
they are directly related, like this: 

[Evolution] Issue with read only calendars using CalDav SSL (3.10.4)
- http://marc.info/?l=evolution&m=140983877609485&w=2

evolution: CalDAV calendars marked "read-only" incorrectly, fixed upstream
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=771868

FIY my calendar server is SOGo (2.2.9a). 

my evolution packages:
evolution-data-server-3.12.11-8.4.x86_64
evolution-3.12.11-8.1.x86_64
evolution-data-server-lang-3.12.11-8.4.noarch