“Define the key for this EntityType.” when including attribute of type ApplicationUser

Question

I'm writing C#/ASP.NET MVC5 web application, and I'm hitting the following errors when I try to do a new migration

ToTheMoon.DAL.IdentityUserLogin: : EntityType 'IdentityUserLogin' has no key defined. Define the key for this EntityType.
ToTheMoon.DAL.IdentityUserRole: : EntityType 'IdentityUserRole' has no key defined. Define the key for this EntityType.
IdentityUserLogins: EntityType: EntitySet 'IdentityUserLogins' is based on type 'IdentityUserLogin' that has no keys defined.
IdentityUserRoles: EntityType: EntitySet 'IdentityUserRoles' is based on type 'IdentityUserRole' that has no keys defined.

I have included a property(?) of type ApplicationUser in one of my models. I believe that this is what's causing it:

public ApplicationUser Requester { get; set; }

I am well aware of the fact that—in general—I should explicitly mark something as a key with the [Key] annotation, but I don't believe this applies as the error messages are describing classes that are part of MVC5's 'batteries included' login system.

I have seen something about this being caused by incorrectly overriding a method (can't remember what one it is now), but I'm not doing that, so all other questions that I've found online are useless to me.

Anything is appreciated.

EDIT: Here's my context, it's pretty bare.

public class ApplicationDbContext : IdentityDbContext<ApplicationUser>
{
    public ApplicationDbContext() : base("DefaultConnection") { }
}

Answer 1

From the comments in the Question:

It appears the entity that added the ApplicationUser Requester property is defined in a different context. Because it is in a different context that context knows nothing about the configurations for all of the Identity entities, since that is set up by the IdentityDbContext.OnModelCreating method.