Auto accept invited calendar event

For planning common rooms occupation we use dedicated accounts with shared calendars. When we want to book an event in a such room, we create it in personal calendar, invite members and shared calendar account too. It should automatically accept the invitation and add it in its calendar.

This was somehow set in server and work until now. We do not know how to set it for new calendars. You may do know? (IWDC2, Centos 7)