MM-60717: add OffWork to presence detection (#750)

If a user chooses to "Appear Offline", treat this like do we do when the
user is manually away and start delivering messages to Mattermost.

Fixes: https://mattermost.atlassian.net/browse/MM-60717

server/presence.go

@@ -41,7 +41,7 @@ func userPresenceIsActive(presence clientmodels.Presence) bool {
 
 	// Explicitly handle known activity states for being inactive or away.
 	switch presence.Activity {
-	case PresenceActivityOffline, PresenceActivityInactive, PresenceActivityAway:
+	case PresenceActivityOffline, PresenceActivityOffWork, PresenceActivityInactive, PresenceActivityAway:
 		return false
 	}