title: How to send user details to backend API if client user was authenticated at the API Management service front end?
body: <p>I'm interested in using Azure APIMS to authenticate requests from a client app using Azure AD. However, I am interested in having the backend API know details about the user who was authenticated at the gateway such that I can perform logic based on that user. </p>
  
  <p>Backend API would be ASP.NET Core 3.x web api. </p>
  
  <p>What approaches are available to me?
  One thing I can think of off the top of my head is to simply forward the Authentication header along to the backend API, and do some type of lookup there. But I am wondering if there is any way for me to aggregate the user details at the frontend api gateway layer, and pass that information along in a header?</p>
  
  <p>How are backend applications obtaining details about the authenticated user when requests are authenticated at the frontend gateway layer?</p>
  
  <p>I realize that if I was to add authentication at the backend API layer (which would duplicate the authentication/authorization) I may be able to technically accomplish it this way. However, this would violate the SRP principle and perhaps add some necessary overhead to the backend. </p>