Design appointment scheduling data model and APIs

## Scenario You are extending an existing healthcare system that already has **User** and **Patient** management APIs. - **Doctors** and **Staff** are **Users**. - **Patients are not Users** (they are separate entities managed via Patient APIs). - You must add an **Appointment Scheduling** capability between **Doctors** and **Patients** at **Hospitals**. - Implementation context: **Django** (data model design + REST API design). ## Definitions & Business Rules ### Hospital operating hours - Each **Hospital** has operating hours (e.g., 09:00–19:00). - The schedule UI only displays hours when the hospital is open. ### Doctor Availability - An **Availability** is a time range when a **Doctor** can see patients **at a specific Hospital**. - A Doctor can only have Availabilities **within the Hospital operating hours**. - Users (staff) can create Availabilities for doctors. ### Appointment - An **Appointment** is a time when a **Patient** is scheduled to see a **Doctor** at a **Hospital**. - Appointments are: - exactly **1 hour** long - must **start on the hour** (e.g., 10:00, 11:00) - An Appointment can only be scheduled **within an Availability**. - Users (staff) can create Appointments between Doctors and Patients. ## UX-driven behavior - Clicking an **empty time slot** prompts the user to schedule an **Availability**. - Clicking an **Availability** prompts the user to schedule an **Appointment**. ## Required API capabilities (Gherkin-style) 1. **View** Availabilities and Appointments filtered by: - date - doctor(s) - hospital 2. **Create** a Doctor’s Availability for a given date and hospital. 3. **Create** an Appointment within an Availability. ## Your task Design: 1. A Django-friendly **data model** (entities, key fields, relationships, constraints). 2. The **REST APIs** (endpoints, request/response shapes, validation rules, error cases). 3. The core logic to enforce constraints (operating hours, no invalid times, appointment-within-availability, conflict handling).