Allow business owner to make any session or time slot unavailable

Currently a session would need to be deleted or moved into the past, or a time slot ‘filled up’ in order for them to be un-bookable.

This new feature would allow the user to make that session or time slot ‘unavailble’ - this is a new status that would remove it from the booking widget as a booking option, but it would still appear on the back-end, greyed out or otherwise marked as currently unavailable, with the option to make it available again should that be required.