Eventbrite integration improvements grouping

[conoramurphy-zz]

This is a ticket a holding for Eventbrite improvements until a decision is made to cull/expand them.

• [ ] Embedded event using EB redirect to Zen booking as well as EB
• [ ] Eventbrite integration isn't clear that only future events will appear (no initial sync)
• [ ] Eventbrite integration doesn't support multiple webhook per account (?)
• [ ] Create a mailing list that cuts anyone who created an event in the last 3 months and hasn't linked in Eventbrite
• [ ] Investigate handling of deletion of events in EB integration
• [ ] Eventbrite multiple eventbrite locations
• [ ] Investigate handling of series in EB integration
• [ ] Investigate and decide how to handle EB eventseries