Add substitute pool/on-call times
Teachers are available on certain days, so they are prioritized compared to other teachers regarding the completion of substitute hours
- Allow entering of on-call hours for individual teachers
- Priority system when selecting substitute teacher for one lesson with assistance function: Prioritize on-call teachers, teachers with hours before/after the lesson to be substituted, free teachers, teachers with fitting subjects → Develop constraint system that calculates a ranked list of fitting teachers for a specific lesson in need of a substitution