问题 I am looking to build an appointment booking app with the following characteristics: - Users can be service providers or buyers - Service providers set their availabilities (but can only set their availabilities at a maximum of 6 months ahead) - Buyers can then book appointments based on those availabilities - each appointment, based on the type of service, takes a different amount of time - Based on the appointment that a buyer selects, a different set of availabilities is shown depending on