title: IdentityServer3 - 401 Unauthorized when calling Identity API Controller
body: <p>I have a project which uses IdentityServer3 for Auth as a Service. </p>
  
  <p>Recently I was tasked with creating a seamless experience for End-Users to edit their identity information. </p>
  
  <p>I did this by creating an API Controller in my application which uses a HTTPClient to call another API Controller living in my IdentityServer project. It basically exposes the Identity management methods to the world, but "passes-through" any requests on to the IdentityServer Api. </p>
  
  <p>All is well right up until I call the IdentityServer Api Controller. My breakpoint there is never hit, regardless of the presence of a "Authorize" attribute. I end up receiving a "401: Unauthorized" back from the IdentityServer Api controller. </p>
  
  <p>I've tried to reuse the original request's Auth headers, but that didn't work. I also tried to find a "access_token" claim from my claim principle, but one wasn't found. </p>
  
  <p>here is a code snippet: </p>
  
  <pre><code>            var httpClient = new HttpClient();
  
              // this didn't work - tried reusing the auth from the original request
              //httpClient.DefaultRequestHeaders.Authorization = request.Headers.Authorization;
  
              // this didn't work either - "access_token" is not found 
              //httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("bearer", Caller.FindFirst("access_token").Value);
              var routePrefix = GetRoutePrefix();
  
              var response = await httpClient.PostAsync(
                         $"{routePrefix}/post",
                         new ObjectContent(typeof(TDObj), entity, new JsonMediaTypeFormatter()));
  
              return response;
  </code></pre>
  
  <p>I'm new to IdentityServer3 and OAuth and not sure what to do next. I tried creating a new scope for "identity" and tried to make it a required scope in my client application, but that didn't seem to do the trick. I know I'm missing some key piece of understanding here, but there is so much documentation for IdentityServer, I don't know where to begin and can't find anything specific to this need. I'm in the weeds! Can anyone help me understand what's going on here? Thanks! </p>