title: Modify content of response when using [Authorize]-attribute in dotnet core 3.0
body: <p>We're using the <code>[Microsoft.AspNetCore.Authorization.Authorize]</code>-attribute to authorize requests to our api. If the JWT is not present or invalid in the HTTP-Header, a 401-error is returned. We want to modify to response body to contain more information, rather than an empty body. We've tried doing the following thing:</p>
  
  <pre><code> app.Use(async (context, next) =&gt;
   {
       var statusCode = context.Response.StatusCode;
       //write a custom body here       
   });
  </code></pre>
  
  <p>But the status code is always <code>HTTP.200</code> which seems to me a bit strange since Postman tells me that it is a <code>HTTP.401</code></p>
  
  <p>In case of an exception being thrown in our api, we have implemented a filter which implements <code>IActionFilter</code> to return a more detailed error message. This is what we are looking for to do in case of an <code>HTTP.401</code>. Is there any filter I can add to achieve this? </p>