Events are often scheduled before the platform (Zoom link, Slack
channel) is chosen. The current workaround is a placeholder URL like
"https://us02web.zoom.us/j/TBD", which leaks to the public page as a
broken link.
Accept the literal "TBD" (case-insensitive) in both the Mongoose
validator and the form-side validator. The public detail page renders
"Platform TBD" instead of a link when the location matches.