I introduced a flag in the ctor to synchronize presence changes in the users lookup table. It's an opt-in option because it can have a negative impact on performance.
I introduced a SubscribePresenceChange method to subscribe changes only for specific users
I added OnPresenceChanged event
I added support of manual_presence_change event (same OnPresenceChanged event is raised)
I fixed the SendPresence method (the argument was not used)
Presence changes support is broken in SlackApi probably because of changes on Slack in January 2018 (https://api.slack.com/events/presence_change).
SubscribePresenceChangemethod to subscribe changes only for specific usersOnPresenceChangedeventmanual_presence_changeevent (sameOnPresenceChangedevent is raised)SendPresencemethod (the argument was not used)