- hivepress-bookings has no guests field; the places booked are stored as
hp_quantity (only when "Allow multiple places" is enabled)
- Verified against hivepress-bookings 1.5.5: start_time / end_time were
already correct and stay unchanged
Verify: vendor/bin/phpunit --filter test_on_register_fields_uses_real_booking_meta_keys;
addon unit 155 OK, integration 57 OK
PR: PR-009