title: Claims transformation support missing in ASP.NET Core 2.0
body: <p>I am using JWT Bearer auth in my new asp.net core 2.0 api app and want to add some extra claims to the current identity. This extra info is located in another api which need to be queried. My understanding is that claims transformation would be the proper place to do this. In .net core 1.1 you have the IClaimsTransformer interface in Microsoft.AspNetCore.Authentication nuget package, but I cannot install this one in my .net core 2.0 app. Is there a alternative way to transform claims in asp.net core 2.0 and is this the correct approach for my use case?</p>