✅ List<KeyValuePair<Trader, long>> requires primary key to be defined

public class Item
{
    [Key]
    public int Id { get; set; }
    public string Name { get; set; }
    public List<KeyValuePair<Trader, long>> TraderPrices { get; set; }
}

[Keyless]
public class Trader
{
    public int Id { get; set; }
    public string Name { get; set; }
    public bool IsTeTrader { get; set; }
    public bool IsAwTrader { get; set; }
}

class ItemDb : DbContext
{
    public ItemDb(DbContextOptions<ItemDb> options)
        : base(options) { }
    
    public DbSet<Item> Items => Set<Item>();
}

db.Items.Add(itemInput);
await db.SaveChangesAsync();
return Results.Created($"/items/{itemInput.Id}", itemInput);