SGRH.Api/              # Presentation Layer - REST API Controllers
SGRH.Application/      # Application Layer - Use Cases (CQRS)
SGRH.Domain/           # Domain Layer - Business Logic & Entities
SGRH.Infrastructure/   # Infrastructure - External Services (S3, SES)
SGRH.Persistence/      # Persistence - EF Core & Repositories
SGRH.Auth/             # Authentication & Authorization

public abstract class EntityBase
{
    protected abstract object GetKey();

    public override bool Equals(object? obj)
    {
        if (obj is not EntityBase other) return false;
        if (ReferenceEquals(this, other)) return true;
        if (GetType() != other.GetType()) return false;
        return GetKey().Equals(other.GetKey());
    }

    public override int GetHashCode() => GetKey().GetHashCode();
}

public static class Guard
{
    public static void AgainstNullOrWhiteSpace(string? value, string name, int maxLength)
    {
        if (string.IsNullOrWhiteSpace(value))
            throw new ValidationException($"{name} no puede estar vacío.");

        if (value.Length > maxLength)
            throw new ValidationException($"{name} supera el máximo de {maxLength} caracteres.");
    }

    public static void AgainstOutOfRange(int value, string name, int minExclusive)
    {
        if (value <= minExclusive)
            throw new ValidationException($"{name} debe ser mayor a {minExclusive}.");
    }
}

public interface IReservaDomainPolicy
{
    int? GetTemporadaId(DateTime fechaEntrada);
    void EnsureHabitacionDisponible(int habitacionId, DateTime fechaEntrada, 
                                     DateTime fechaSalida, int? reservaId);
    void EnsureHabitacionNoEnMantenimiento(int habitacionId, DateTime fechaEntrada, 
                                           DateTime fechaSalida);
    decimal GetTarifaAplicada(int habitacionId, DateTime fechaEntrada);
    void EnsureServicioDisponibleEnTemporada(int servicioAdicionalId, int? temporadaId);
    decimal GetPrecioServicioAplicado(int reservaId, int servicioAdicionalId);
}