When authenticating a user, you might want to persist the state through the authentication request – for example whether the user is authenticating for some special action like organizational signup or simply some state of your application. ASP.NET Core makes this very easy.
We have been migrating couple of projects to ASP.NET Core 2.0 recently. Amongst the major changes in ASP.NET Core 2.0, probably the biggest change has been done in the Authentication. I have written an article about cookie size in ASP.NET Core which explains the basic issue with too many claims in the identity. ASP.NET Core 2.0 OIDC addresses this by removing some of the token values from the identity on the background.