title: Reference to type 'AuthenticationOptions' claims it is defined in 'Microsoft.AspNetCore.Authentication', but it could not be found
body: <p>I'm trying to run 'UseIdentityServerAuthentication' and pass in IdentityServerAuthenticationOptions and get this error in Asp.Net Core 2.</p>
  
  <p>Looking online it appears this was on the roadmap for Asp.Net Core 2 Preview 2, I'm running the latest release version of it so I thought it would be available by now.</p>