Consider some kind of support for recurring events

[zachallaun]

We recently added support for recurring events on recurse.com/calendar. When you RSVP for one of these events, you have to choose whether you're RSVPing for a single event, all following events, or all events in a recurring series.

However, it's not obvious what would happen if you used rsvp yes in Zulip for one of these events. Would it RSVP you to only that one? To all events in that series?

We weren't sure what to do, so for now RSVPBot doesn't actually announce/interact with any recurring events, which is definitely a bummer.

[WesleyAC]

IMO what makes the most sense is having rsvp yes RSVP to all by default (with a message saying that that's what happened), and also have rsvp yes once and rsvp yes all for when you want to be explicit.

The logic behind this is that it's less of an annoyance to get a notification about something you don't want to go to than it is to not get a notification about something you do want to go to.

However, the highest priority thing for me (besides a reasonable error message) is making rsvp ping work for recurring events. For ping, there is a clearly correct option, so it's frustrating to not have it implemented.

I'm happy to work on any of these issues, but I'm having trouble finding the part of the codebase where an exception is raised from executing a command on a recurring event. Can someone point me to the right part of the codebase to find that?