title: IdentityUserLogin<string>' requires a primary key to be defined error while adding migration
body: <p>I am using 2 different Dbcontexts. i want to use 2 different databases users and mycontext. While doing that i am getting a error The entity type 'Microsoft.AspNetCore.Identity.EntityFrameworkCore.IdentityUserLogin' requires a primary key to be defined. I think there is something wrong with IdentityUser please suggest me where can i change my code so that i can add migration.</p>
  
  <p>My Dbcontext class:</p>
  
  <pre><code> class MyContext : DbContext
  {
      public DbSet&lt;Post&gt; Posts { get; set; }
      public DbSet&lt;Tag&gt; Tags { get; set; }
  
      protected override void OnModelCreating(ModelBuilder modelBuilder)
      {
          base.OnModelCreating(modelBuilder);
  
          modelBuilder.Entity&lt;PostTag&gt;()
              .HasKey(t =&gt; new { t.PostId, t.TagId });
  
          modelBuilder.Entity&lt;PostTag&gt;()
              .HasOne(pt =&gt; pt.Post)
              .WithMany(p =&gt; p.PostTags)
              .HasForeignKey(pt =&gt; pt.PostId);
  
          modelBuilder.Entity&lt;PostTag&gt;()
              .HasOne(pt =&gt; pt.Tag)
              .WithMany(t =&gt; t.PostTags)
              .HasForeignKey(pt =&gt; pt.TagId);
      }
  }
  
  public class Post
  {
      public int PostId { get; set; }
      public string Title { get; set; }
      public AppUser User {get; set;}
      public string Content { get; set; }
  
      public List&lt;PostTag&gt; PostTags { get; set; }
  }
  
  public class Tag
  {
      public string TagId { get; set; }
  
      public List&lt;PostTag&gt; PostTags { get; set; }
  }
  
  public class PostTag
  {
      public int PostId { get; set; }
      public Post Post { get; set; }
  
      public string TagId { get; set; }
      public Tag Tag { get; set; }
  }
  </code></pre>
  
  <p>and AppUser class:</p>
  
  <pre><code>public class AppUser : IdentityUser
  {
    //some other propeties
  }
  </code></pre>
  
  <p>when I try to Add migration the following error occurs.</p>
  
  <pre><code>The entity type 'Microsoft.AspNetCore.Identity.EntityFrameworkCore.IdentityUserLogin&lt;string&gt;' requires a primary key to be defined.
  </code></pre>
  
  <p>give me solution to resolve the issue..</p>