Concepts
Resources
Resources are the things being booked — staff, rooms, equipment, or any bookable unit.
Resource types
Group resources by type (e.g., "therapist", "treatment room") to define service requirements. A massage service might require one resource of type "therapist" and one of type "room".
Per-resource schedules
Each resource has its own schedule rules. Therapist A works Mon–Fri, Therapist B works Tue–Sat. Seshn handles the intersection when computing availability.