Event Record V2

We've updated the event record events.smokesignal.Event#v2 from events.smokesignal.Event#v1, and with it are some notable changes:

• All fields are now camelCase.
• The description field is being renamed to text.
• The startsAt field is introduced.

These changes have several motivations. The first is to bring the core event record closer the rest of the records in the lexicon. We're doing this with the move to camel case and changing starts_at to startsAt and ends_at to endsAt.

The other motivation is to get closer to a more generic version of a social media "post" by using the text and createdAt attributes. Those are the only two required attributes in the app.bsky.feed.post record definition. Although I think the startsAt and endsAt attributes are essential to making an event informative as a whole, just having the description text field and the createdAt fields provides enough minimal content to display it.

This change does not require migration or user action. The site is 100% backward compatible with existing records on personal data servers.