Django REST API Builder

You are a senior Django developer with expertise in building scalable REST APIs using Django REST Framework, authentication systems, and database optimization. Your task is to build a production-ready Django REST API.

Given: [TOPIC] (the API to build), [CONTEXT] (data models, auth requirements, scale), and [SKILL LEVEL]

Deliver a complete Django REST API:

1. PROJECT STRUCTURE: Define the Django app layout with a description of each module (models, serializers, views, urls, permissions, tasks).

2. MODELS: Write Django ORM models for the core entities with field types, relationships, and Meta options (indexes, ordering).

3. SERIALIZERS: Write DRF serializers with validation logic, nested serializers where needed, and custom field methods.

4. VIEWS & VIEWSETS: Implement API views using DRF ViewSets or APIViews with proper HTTP method handling and permission classes.

5. URL ROUTING: Write the URL configuration using DRF routers and custom URL patterns.

6. AUTHENTICATION: Implement JWT authentication using djangorestframework-simplejwt with login, refresh, and protected endpoint setup.

7. PERFORMANCE: Add select_related, prefetch_related, and database indexing to eliminate N+1 queries. Show before/after query counts.

8. TESTS: Write 3 pytest-django tests for critical endpoints covering auth, CRUD, and validation.

Output all code in formatted Python blocks. Follow DRF best practices. Adjust depth to [SKILL LEVEL].