Add feature to allow students to preview scheduler but not sign up for slots until specified date

It would be helpful in some use cases for students to be able to preview a scheduler but not be able to sign up for slots until a set date.

This could be a simple setting addition of a Scheduler setting: a checkbox -> when checked, enable a date/time picker. The text for this setting could be "Prevent student bookings until specified date."

This would allow students to preview all of the scheduler slots to have an idea of what their schedule may look like when the bookings open, in the case of time-sensitive bookings. Kind of like when music concert tickets go on sale.