marechai/Marechai.Database/Models/PeopleByBook.cs

using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace Marechai.Database.Models
{
    public class PeopleByBook : BaseModel<long>
    {
        public int  PersonId { get; set; }
        public long BookId   { get; set; }
        [Column(TypeName = "char(3)")]
        [Required]
        public string RoleId { get; set; }

        public virtual DocumentPerson Person { get; set; }
        public virtual Book           Book   { get; set; }
        public virtual DocumentRole   Role   { get; set; }
    }
}