title: Join table not being created when adding a list of IdentityUser to an entity in Entity Framework Core
body: <p>I have two different types of users that have different properties so I created 2 new classes and each of them inherit from <code>AppUser</code>. I am aware that EF uses a discriminator column in the <code>AspNetUsers</code> table when doing this. Additionally, a student has many teachers so I expect a join table to be created that will have <code>TeacherUserId</code> and <code>StudentId</code>.</p>
  
  <p>When I run <code>Update-Database</code>, it adds a <code>StudentId</code> column to the <code>AspNetUsers</code> table.</p>
  
  <p>Where is my <code>StudentTeachers</code> table? It seems like it is trying to handle it in <code>AspNetUsers</code> table with many rows which would be horrible. I don't want to create a new identity user for every single <code>student.teacher</code>.</p>
  
  <p>Here are my model classes:</p>
  
  <pre><code>public class AppUser : IdentityUser
  {
      public string FirstName { get; set; }
      public string MiddleName { get; set; }
      public string LastName { get; set; }
  }
  
  public class TeacherUser : AppUser
  {
      public string TeacherSpecificProperty { get; set };
  }
  
  public class StudentUser : AppUser
  {
      public string StudentSpecificProperty { get; set };
  }
  
  public class Student
  {
      public Student()
      {
          this.Teachers= new List&lt;TeacherUser&gt;();
      }
  
      public int Id { get; set; }
      public string FirstName { get; set; }
      public string LastName { get; set; }
      public List&lt;TeacherUser&gt; Teachers{ get; set; }
  }
  </code></pre>