* Present: we know a buddy has joined either by ActivitiesChanged in BuddyInfo when we aren't in this activity, or by GetAllMembers in org.freedesktop.Telepathy.Channel.Interface.Group if we are already in. We also emit this signal for each buddy in an activity that has become valid.
−
* Future:
+
* Future: BuddyJoined is deprecated by BuddyHandleJoined