升级到.NET核心3.1:替换UserManager.NormalizeKey方法？

public class CustomUserManager<TUser> : UserManager<TUser> where TUser : class
{
    public CustomUserManager(IUserStore<TUser> store, IOptions<IdentityOptions> optionsAccessor,
        IPasswordHasher<TUser> passwordHasher, IEnumerable<IUserValidator<TUser>> userValidators,
        IEnumerable<IPasswordValidator<TUser>> passwordValidators, ILookupNormalizer keyNormalizer,
        IdentityErrorDescriber errors, IServiceProvider services, ILogger<UserManager<TUser>> logger)
        : base(store, optionsAccessor, passwordHasher, userValidators, passwordValidators,
               keyNormalizer, errors, services, logger)
    {
    }

    public override string NormalizeKey(string key)
    {
        // 自定义NormalizeKey方法的实现，可以使用各种字符串处理函数或算法
        return key.ToLower();
    }
}