title: Authenticate users to azure function when user is authenticated in web app
body: <p>I have an ASP.NET MVC Web Application running as a web app in Azure App Service. This web app calls an Azure Function via HttpClient from a Controller. Authentication/Authorization is configured in the web app with Azure Active Directory. I need the user to also be authenticated when a call to the Azure Function is made so that I can access the user Claims.
  I tried to also configure Authentication in the Azure Function itself but this resulted in an "Unauthorized response" whenever I called the function from my web app.
  Is there a way to make both the web app and the Azure function use the same Active Directory Authentication. So that when a user is authenticated to the web app, he does not need to authenticate again in the Azure function and all the User Claims would be available in the function itself?</p>