[Bug] Hide / freeze ticket sales after event ends

[brianfeister]

TLDR; you can buy tickets for an event that happened months or years ago right now, let's fix this.

In general, we might want to require an endTime conditionally (from the event admin UI) for paid events so we know when the event ends and can automatically disable ticket sales at that time

"Event Series" is where this gets more interesting, as the series could easily span 6 months. We want to error on the permissive side (which means more opportunity for event organizers to make money) and let people buy tickets to a series all the way through the end of the last instance in the series. That would mean checking in the UI that the last event instance and the parent "series" event share an endTime when creating an event.

A "fallback" behavior could be to keep endTime as optional for single (non-series) events and just close tickets 1 hour after the startTime and call that good.

Here is an example of a "series parent" https://meetnear.me/event/73a72ca2-2205-4ebe-adec-75c114c8ca8a