[RFC] Events: announce a stream and remind followers before it starts #1440

I'd like to propose events: announce something you're about to do, like a stream at 8 pm, so the people who follow you can sign up for a reminder, the way YouTube's "Notify me" works for upcoming premieres and streams.

The screenshots below are from a quick prototype on a local copy, so every other user is made up.

Why?

• "Go live" only helps once you're already live. The red ring reaches whoever happens to open /dev/null while you're streaming. If you're live for an hour at 8 pm, most of your followers find out at 9.
• Today people announce a stream with a plain commit ("live at 8 pm CET!"). Readers have to remember it, and convert the time zone themselves. Nothing reminds them when it starts.
• Most of what it needs is already here. Polls show how to attach something to a commit, scheduled commits and "Go live" already have the time and stream-link rules, and the scheduler already runs every minute.

Ideas

Creating an event

In the composer, next to Add poll, an Add event control takes:

• Title: up to 80 characters
• Starts at: a future time within 30 days, in five-minute steps, like scheduled commits
• Link (optional): a YouTube or Twitch stream, checked with the same rules as Go live

Same rules as a poll: top-level commits only, no images or poll alongside it, and no replies or quotes. The event opens when its commit is approved. Scheduling a commit that has an event works as usual.

Every event is a commit

Like a poll, the event belongs to a commit, so it shows up in Following, Latest and Trending without a new feed. Stars, replies, mutes and blocks all work through the commit. The card shows:

• the title, and the start time in the reader's time zone ("Today, 8:00 PM", or "Starts in 12 min" when it's close)
• a Remind me button with a count, e.g. "42 interested"
• once it starts: Live now with a Watch button if it has a link, and Ended later on

Remind me

• It's one tap, and tapping again cancels it. There's no Going / Maybe / Not going, since the button only exists for the reminder.
• Any signed-in reader can use it, except the author.
• The author sees the count. Like poll voters, the people who signed up stay private.

The reminder

5 minutes before the start, everyone who tapped Remind me gets an Event starting notification (under All). It links to the stream when there is one, and to the commit otherwise. A scheduled job checks every minute and sends each reminder once. Mutes, blocks, and deleted or rejected commits stop it, same as other notifications.

Going live automatically

If the event has a stream link, the author's Go live status turns on at the start time, so the red ring appears without a click. It ends after 2 hours by default, and End stream works as usual.

Changing or cancelling

To change the time, delete the commit and post a new one, the same way you change a scheduled commit. Deleting the commit cancels the event, and nobody gets a reminder for it.

Out of scope for a first version

• Off-site (push) reminders. Off-site notifications only cover Remotes for now, and contain no content. On-site reminders reach whoever has /dev/null open. Push reminders would be a follow-up.
• Recurring events, events that aren't streams, calendar (.ics) export, and events posted as an organization.

Open questions

1. Should a follower get an "Event starting" notification even without tapping Remind me, like YouTube subscribers do? That would reach more people, but it risks spam for people who follow many streamers.
2. Is 5 minutes the right lead time, or should we also send one an hour before?
3. Should the automatic Go live be opt-in when creating the event?

Happy to build this if it sounds good.