Use custom status for "In a meeting" user state

At the moment we give the user two options to have their status automatically set to "Away" or "Do not Disturb". Ideally we incorporate the new Custom Status feature that allows us to use a Calendar emoji and message to note that the user is in a meeting.

We can incorporate the meeting end time in the custom status message, something like "In a meeting until 10:00AM EDT", using whatever timezone the user that is in the meeting. This can't be adapted to the user that is viewing the status, because this message is constructed once, to set the custom status.