Create comprehensive FastAPI multi-database template

[Copilot]

This PR implements a complete FastAPI template that demonstrates how to build modern, production-ready APIs with support for multiple database backends: MongoDB, MySQL, and PostgreSQL.

What's New

This template provides a production-ready foundation for FastAPI applications with comprehensive multi-database support:

🏗️ Project Structure

• Clean, modular architecture with separate packages for API routes, database connections, models, and configuration
• 17 Python files organized following FastAPI best practices
• Professional project layout that scales well

🚀 Technology Stack

• FastAPI with async/await support and automatic API documentation
• MongoDB integration using Motor (async driver) for document storage
• MySQL integration using aiomysql (async driver) for relational data
• PostgreSQL integration using asyncpg (async driver) for advanced relational features
• Pydantic models for data validation and type safety
• Docker & Docker Compose for complete containerization

📊 Database Examples

Each database demonstrates different use cases with complete CRUD operations:

• MongoDB (Users): Document-based user management with email validation
• MySQL (Products): Relational product catalog with pricing and categories
• PostgreSQL (Orders): Complex order management with foreign key relationships

🛠️ Developer Experience

• Auto-generated Documentation: Swagger UI and ReDoc interfaces
• Health Monitoring: Individual database connectivity checks
• Environment Configuration: Flexible setup via environment variables
• Comprehensive Error Handling: Proper HTTP status codes and error messages
• Type Safety: Full type hints throughout the codebase
• Development Tools: Makefile, dev requirements, and validation scripts

📚 Documentation & Examples

• Comprehensive README: Complete setup and usage instructions
• Quick Start Guide: Get running in minutes
• API Examples: Practical curl commands, Python, and JavaScript examples
• Interactive Demo: Script that showcases all template features

🐳 Deployment Ready

• Docker Compose: Start all services (API + 3 databases) with one command
• Production Considerations: CORS configuration, security settings, logging
• Health Endpoints: Monitor application and database status

Example Usage

# Quick start
git clone <repo>
cd fastapi-mongo-mysql-postgresql-api
docker-compose up -d
python main.py

# Visit http://localhost:8000/docs for interactive API documentation

The template includes practical examples for each database:

# Create a user in MongoDB
POST /mongodb/users
{
  "name": "John Doe",
  "email": "john@example.com", 
  "age": 30
}

# Create a product in MySQL
POST /mysql/products
{
  "name": "Laptop",
  "price": 999.99,
  "category": "Electronics"
}

# Create an order in PostgreSQL
POST /postgresql/orders
{
  "user_id": "user-uuid",
  "product_id": "product-uuid",
  "quantity": 2,
  "total_amount": 1999.98
}

Validation

The template includes validation tests that confirm:

• ✅ All imports work correctly
• ✅ Pydantic models validate properly
• ✅ Configuration system is functional
• ✅ FastAPI application structure is valid
• ✅ No deprecation warnings
• ✅ Clean, maintainable code

This template serves as an excellent starting point for building scalable FastAPI applications that need to work with multiple database technologies, demonstrating modern Python development practices and production-ready patterns.

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