New resource type representing all the calls (meeetings and common calls) with change notifications

We plan to build some analytics on top of information about the user's participation in calls and meetings. We want to build those analytics in near real-time. To do that we need a new resource type representing any call itself with something like an attendee report. ie with the exact time when all participants joined or left the call. We need to have a change notification for that resource also. The desired schema is the following: when some user created a call notification about call creation received; when the second user accepts the call notification about update received with his joining time; when the third user joined the conference another update notification is received.  and so on.