//EF Core creates duplicates of joining table of many to many relation.
//I'm using EF Core dbcontext based on IdentityDbContext
//With 3 related models:

    public class User : IdentityUser<Guid>
    {
        public override string UserName { get; set; }
        [AdaptIgnore]
        public override string NormalizedUserName { get; set; }
        public override string Email { get; set; }
        [AdaptIgnore]
        public override string NormalizedEmail { get; set; }
        [AdaptIgnore]
        public override bool EmailConfirmed { get; set; }
        [AdaptIgnore]
        public override string PasswordHash { get; set; }
        [AdaptIgnore]
        public override string SecurityStamp { get; set; }
        [AdaptIgnore]
        public override string ConcurrencyStamp { get; set; }
        [AdaptIgnore]
        public override string PhoneNumber { get; set; }
        [AdaptIgnore]
        public override bool PhoneNumberConfirmed { get; set; }
        [AdaptIgnore]
        public override bool TwoFactorEnabled { get; set; }
        [AdaptIgnore]
        public override DateTimeOffset? LockoutEnd { get; set; }
        [AdaptIgnore]
        public override bool LockoutEnabled { get; set; }
        [AdaptIgnore]
        public override int AccessFailedCount { get; set; }
        [AdaptIgnore]
        public List<Role> Roles { get; set; }
    }



    public class Role : IdentityRole<Guid>
    {

        public override string Name { get; set; }
        [AdaptIgnore]
        public override string NormalizedName { get; set; }
        [AdaptIgnore]
        public override string ConcurrencyStamp { get; set; } = Guid.NewGuid().ToString();
        public List<User> Users { get; set; }
    }



    public class UserRole : IdentityUserRole<Guid>
    {
        public override Guid UserId { get; set; }
        public override Guid RoleId { get; set; }
    }

//It Creates duplicates in migration:

            migrationBuilder.CreateTable(
                name: "RoleUser",
                columns: table => new
                {
                    RolesId = table.Column<Guid>(type: "uuid", nullable: false),
                    UsersId = table.Column<Guid>(type: "uuid", nullable: false)
                },
                constraints: table =>
                {
                    table.PrimaryKey("PK_RoleUser", x => new { x.RolesId, x.UsersId });
                    table.ForeignKey(
                        name: "FK_RoleUser_Roles_RolesId",
                        column: x => x.RolesId,
                        principalTable: "Roles",
                        principalColumn: "Id",
                        onDelete: ReferentialAction.Cascade);
                    table.ForeignKey(
                        name: "FK_RoleUser_Users_UsersId",
                        column: x => x.UsersId,
                        principalTable: "Users",
                        principalColumn: "Id",
                        onDelete: ReferentialAction.Cascade);
                });


migrationBuilder.CreateTable(
                name: "UserRoles",
                columns: table => new
                {
                    UserId = table.Column<Guid>(type: "uuid", nullable: false),
                    RoleId = table.Column<Guid>(type: "uuid", nullable: false)
                },
                constraints: table =>
                {
                    table.PrimaryKey("PK_UserRoles", x => new { x.UserId, x.RoleId });
                    table.ForeignKey(
                        name: "FK_UserRoles_Roles_RoleId",
                        column: x => x.RoleId,
                        principalTable: "Roles",
                        principalColumn: "Id",
                        onDelete: ReferentialAction.Cascade);
                    table.ForeignKey(
                        name: "FK_UserRoles_Users_UserId",
                        column: x => x.UserId,
                        principalTable: "Users",
                        principalColumn: "Id",
                        onDelete: ReferentialAction.Cascade);
                });