getAvailableDates(listing: Listing,holidays: Holiday[],durationOverride?: number,): string[]
Compute available booking dates for a daily listing.
Filters by bookable days of the week and excludes holidays.
For listings with duration_days > 1, excludes start dates whose full range
would hit a non-bookable day or extend past the booking window.
durationOverride lets callers compute availability for a span other than
the listing's stored duration_days — used for "customisable days" listings,
where duration_days is only the maximum, so the date list is built for a
single day (every individually-bookable start) and the chosen span is
validated separately at submit time via isBookingRangeValid.
Returns sorted array of YYYY-MM-DD strings.