HeaderPropagationv3.0.2

ASP.NET Core middleware to propagate HTTP headers from the incoming request to the outgoing HTTP Client requests. This is a backport to ASP.NET Core 2.1 (and 2.2) of the ASP.NET Core HeaderPropagation middleware I had recently contributed to the ASP.NET Core project. All code is licensed under the Apache License, Version 2.0 and copyrighted by the .NET Foundation. If you are using ASP.NET Core 3.0, please use the official package Microsoft.AspNetCore.HeaderPropagation.