Set an expiry time on Appointment Self-booking links

We have had a report from a practice that a link that was sent weeks ago could used to book an appointment which was no longer valid due to changes on the practice side. The test patient didn't receive the email saying the appointment hadn't been booked until after the appointment time elapsed and this has caused concern that a patient may do a similar thing. If an expiry period on the link can be added, then this would reduce the risk of any changes to the appointment schedule before a patient could select a valid appointment slot. This would benefit both patients and staff as patients won't be able to book appointments that they won't be able to attend and staff will be able to easily manage the available appointments