如何将表的主键分配为另一个表的外键

Question

我有两个表：用户和个人资料

public class User
{
    public string Id { get; set; }

    public string UserName { get; set; }
    public string Email { get; set; }
    public string Password { get; set; }

    public Profile Profile { get; set; }
}

public class Profile
{
    public string UserName { get; set; }

    public string FirstName { get; set; }
    public string SecondName { get; set; }
    public DateTime Created { get; set; }

    public User User { get; set; }
}

配置部分：

public class UserConfiguration : EntityTypeConfiguration<User>
{
    public UserConfiguration()
    {
        ToTable( "Users" );

        HasKey( p => p.Id );

        Property( p => p.UserName ).HasMaxLength( 100 );

        Property( p => p.UserName ).HasColumnAnnotation( "Index",
            new IndexAnnotation( new IndexAttribute( "IX_UserName" )
            {
                IsUnique = true
            } ) ).IsRequired();

        // Add code here to relate to Profile table and what code?
        ...
    }
}

public class ProfileConfiguration : EntityTypeConfiguration<Profile>
{
    public ProfileConfiguration()
    {
        ToTable( "Profiles" );

        HasKey( p => p.UserName );

        Property( p => p.FirstName ).HasMaxLength( 100 );
        Property( p => p.SecondName ).HasMaxLength( 100 );
        Property( p => p.Created ).IsRequired();

        // Or add code here to relate to User table and what code?
        ...
    }
}

我需要将两个一对一的表相关联。如何将主键指定为引用 User.UserName 的外键 Profile.UserName ，而不是 User.Id 如何使用Fluent API实现？