Hello,
I was using your solution as a sample, as I'm trying to achive soemthing similar in DNN.
The issue that I'm having is that the HttpContext.Current.GetOwinContext().Authentication.Challenge that called to signin redirects me to the DNN login page instead of the Azure login. That boiled down to the fact that DNN uses forms authentication, and OWIN-OpenId Connect is overtaken by that login.
How did you managed make your module work with DNN website?