We're using this (on a mac) to do 3rd party authentication. The completion handler is getting
Authentication session got error: [The operation couldn’t be completed. (com.apple.AuthenticationServices.WebAuthenticationSession error 1.)], in domain: [com.apple.AuthenticationServices.WebAuthenticationSession]
That seems to be generated if the auth window is closed. However... it's not being closed, so we end up spawning a second one to do it, and this one seems to work.