Admin-only drop-in rates

Admins (aka front desk or coaches) can have a drop-in rate preprogrammed in that only they can access. Intended for session-based programs, and to help any staff know what to charge last minute subs or players that are coming in for only a drop-in, not the entire session. Have this be admin-only, as the program is trying to get sold as a session, but may occasionally make space for drop-in players (at admin discretion)