title: Overriding HTTP request headers via query string
body: <p>We have a client of a ServiceStack service that cannot easily send the correct value for some request headers (such as Accept or Accept-Encoding).</p>
  
  <p>Is there any mechanism in ServiceStack (or ASP.NET) that can allow the client to use query string parameters to override the value of request headers, in a generic way? </p>
  
  <p>The <code>format</code> URL param recognized by ServiceStack is close, but it seems to not help in this specific case (the client needs to send <code>Accept: image/png</code>, which seems to be ignored by the format param).</p>
  
  <p>Or another way to look at this, is there a way to name or annotate the properties of a GET request DTO so that ServiceStack will populate those properties with the values of request headers during deserialization? This could provide an alternative approach for solving this problem.</p>