Warning when class trial/dropin/makeup class scheduled in invalid year

This most likely happens when transitioning to the next year, but it is very easy to forget to select the upcoming year when scheduling a trial, makeup, or drop-in class for the upcoming year. If a studio schedules a student on Dec. 15 for a class in January, the year should either update to the next year OR a warning prompt should be displayed like, "Invalid year. Please select the upcoming year."