Specific Staff Shortcode

Use a shortcode to pre-choose a staff member, so the user won't have to choose a staff member.
Basically admin will be able to choose a staff member for the user.
Use cases: we can embed the shortcode in a staff member profile page.

For example: [bookingpress_form staff=1] [bookingpress_form staff=2] [bookingpress_form staff=3], etc...