Allow separate TKey for the various Identity Entities, like IdentityUser<TUserKey> and IdentityRole<TRoleKey>

[KennethHoff]

Hi,

I was just setting up a new simple Web App by creating simple AspNetCore Identity setup, and I did so by doing what I normally do when I create new domain models; Creating custom Typed identifiers for each domain model, but I quickly realized that, for whatever reason, IdentityUser<TKey>, and IdentityRole<TKey> requires TKey to be the same TKey. This is very annoying and breaks the type-safety of my app.

So I'm wondering; Would it be possible to rework this signature to allow for separate TKey for each entity type?

aspnetcore/src/Identity/EntityFrameworkCore/src/IdentityDbContext.cs

Line 77 in 7f18f8f

public abstract class IdentityDbContext<TUser, TRole, TKey, TUserClaim, TUserRole, TUserLogin, TRoleClaim, TUserToken> : IdentityUserContext<TUser, TKey, TUserClaim, TUserLogin, TUserToken>

For example this:

public abstract class IdentityDbContext<TUser, TUserKey, TRole, TRoleKey, TUserClaim, TUserClaimKey, TUserRole, TUserRoleKey, TUserLogin, TUserLoginKey, TRoleClaim, TRoleClaimKey, TUserToken, TUserTokenKey> : IdentityUserContext<TUser, TUserKey, TUserClaim, TUserClaimKey, TUserLogin, TUserLoginKey, TUserToken, TUserTokenKey>
    where TUser : IdentityUser<TUserKey>
    where TUserKey : IEquatable<TUserKey>
    where TRole : IdentityRole<TRoleKey>
    where TRoleKey : IEquatable<TRoleKey>
    where TUserClaim : IdentityUserClaim<TUserClaimKey>
    where TUserClaimKey : IEquatable<TUserClaimKey>
    where TUserRole : IdentityUserRole<TUserRoleKey>
    where TUserRoleKey : IEquatable<TUserRoleKey>
    where TUserLogin : IdentityUserLogin<TUserLoginKey>
    where TUserLoginKey : IEquatable<TUserLoginKey>
    where TRoleClaim : IdentityRoleClaim<TRoleClaimKey>
    where TRoleClaimKey : IEquatable<TRoleClaimKey>
    where TUserToken : IdentityUserToken<TUserTokenKey>
    where TUserTokenKey : IEquatable<TUserTokenKey>
{
    // ...
}

Most people is probably fine with a simple TKey, but an additional overload that allows for improved type-safety would be very much appreciated.

Assuming dotnet/csharplang#5497 gets implemented before this, you could add a constraint that requires them all to be (explicit) extensions of some base identifier(Say for example, they all have to be Tkey or explicit Extension X for TKey) if that is some fundamental constraint in the Identity system as a whole.