Can not Customize AspNetUsers in ASP.Net Core 2.1.0-preview2-final

In version 2.0.7 - the latest stable version I can customize IdentityUser with this code: 

{
    public class ApplicationUser : IdentityUser
    {
        [Display(Name = "First Name*")]
        [Required]
        public string FirstName { get; set; }

        [Display(Name = "Last Name")]
        public string LastName { get; set; }
        public string Address { get; set; }
        public string City { get; set; }
        public string State { get; set; }
        public string ZipCode { get; set; }
        public string Country { get; set; }
        public int UserMainFunction { get; set; } = 0;
        public DateTime Birthdate { get; set; } = DateTime.UtcNow.AddYears(-35);
    }
}

On ASP.Net Core 2.1.0-preview2-final version, this can not be done. 
AccountContoller and ManageController also are no source any more.

How can we customize them?