Build an Order Processing Microservice

Problem/Feature Description

A food delivery company needs a Spring Boot microservice to handle order processing. Build it using Spring Boot 3 and Java 17+.

Domain concepts:

• Order: id, customerEmail, deliveryAddress, status (PENDING/CONFIRMED/PREPARING/DELIVERED/CANCELLED), totalCents, createdAt
• OrderItem: id, orderId, menuItemId, quantity, unitPriceCents
• MenuItem: id, name, description, priceCents, category, available

Endpoints:

• GET /api/menu -- list all available menu items
• GET /api/menu/:id -- get a single menu item
• POST /api/orders -- place a new order (customerEmail required, at least one item, all items must reference existing available menu items, calculate total automatically)
• GET /api/orders/:id -- get order details including items
• PATCH /api/orders/:id/status -- update order status (only valid transitions: PENDING->CONFIRMED->PREPARING->DELIVERED, or any->CANCELLED)

Business rules:

• Orders can only contain available menu items
• Order total is calculated from item quantities and menu item prices
• Status transitions must follow the allowed flow
• Customer email must be a valid format

Use PostgreSQL as the database (provide the schema, the app does not need to actually connect).

Output Specification

Produce a complete Spring Boot project with:

• Main application class
• All necessary Java source files for the domain logic
• Configuration files
• Database schema
• Test classes for at least the order creation endpoint and status transition logic
• pom.xml with dependencies listed

You may create additional files as needed for a well-structured codebase.