Слоистая архитектура: Presentation → Application → Domain → Infrastructure?

src/
├── Shop.Api/                     # Presentation
│   ├── Endpoints/OrderEndpoints.cs
│   ├── Contracts/CreateOrderRequest.cs
│   └── Program.cs                # composition root: регистрация всех слоёв
├── Shop.Application/             # Application
│   ├── Orders/PlaceOrder/PlaceOrderCommand.cs
│   ├── Orders/PlaceOrder/PlaceOrderHandler.cs
│   └── Abstractions/IOrderRepository.cs, IEmailSender.cs, IUnitOfWork.cs
├── Shop.Domain/                  # Domain — без внешних зависимостей
│   ├── Orders/Order.cs, OrderItem.cs, OrderStatus.cs
│   └── Common/Money.cs, DomainEvent.cs
└── Shop.Infrastructure/          # Infrastructure
    ├── Persistence/ShopDbContext.cs, Configurations/, Repositories/
    ├── Messaging/RabbitMqPublisher.cs
    └── DependencyInjection.cs    # AddInfrastructure(this IServiceCollection ...)
tests/
├── Shop.Domain.Tests/
├── Shop.Application.Tests/
└── Shop.Api.IntegrationTests/

public sealed class Order
{
    private readonly List<OrderItem> _items = [];
    public Guid Id { get; } = Guid.CreateVersion7();
    public OrderStatus Status { get; private set; } = OrderStatus.New;
    public IReadOnlyList<OrderItem> Items => _items;

    public void AddItem(ProductId productId, int qty, Money price)
    {
        if (Status != OrderStatus.New) throw new DomainException("Нельзя менять оплаченный заказ");
        if (qty <= 0) throw new DomainException("Количество должно быть положительным");
        _items.Add(new OrderItem(productId, qty, price));
    }
}

[Fact]
public void Domain_should_not_depend_on_other_layers()
{
    var result = Types.InAssembly(typeof(Order).Assembly)
        .ShouldNot().HaveDependencyOnAny("Shop.Application", "Shop.Infrastructure", "Shop.Api", "Microsoft.EntityFrameworkCore")
        .GetResult();
    Assert.True(result.IsSuccessful, string.Join(", ", result.FailingTypeNames ?? []));
}