aspnetcore: Creation of an Identity User via External Login doesn't set AuthenticationMethod

When signing in with an external provider for the first time, the Default UI for Identity doesn’t set the ClaimTypes.AuthenticationMethod claim.

In ExternalLoginModel<TUser>.OnPostConfirmationAsync, I think the call to SignInAsync should include an authenticationMethod argument, like this:

await _signInManager.SignInAsync(user, isPersistent: false, info.LoginProvider);