Event: rescheduled missing previousStartDate

Name: Fixture Symphony: An Evening of Crawl Patterns
Start: 2026-09-18T19:30:00+01:00
End: 2026-09-18T22:00:00+01:00
Location: Fixture Hall

sb-fixture:sd-event-rescheduled-missing-previousstartdate:served

`eventStatus` set to `EventRescheduled` with no `previousStartDate`.

`eventStatus` is `EventRescheduled` but the required `previousStartDate` is absent