Design the core object-oriented model for a pizza ordering system used by a small restaurant. The system should allow customers to: - browse a menu of pizzas, - customize each pizza by size, crust, and toppings, - place an order containing one or more pizzas, - calculate item prices and the final order total, - choose pickup or delivery, - pay using different payment methods, - track order status such as placed, preparing, baking, ready, and delivered. Discuss the main classes, responsibilities, relationships, and how you would make the design extensible for future features such as promotions or additional menu items.