NuGet v3 responses should support including X-Nuget-Warning response header

NuGet registries can return diagnostic messages in a special HTTP header called X-NuGet-Warning

https://github.com/NuGet/Home/wiki/%5BSpec%5D-Server-side-warnings-for-NuGet-client

The client will optionally display the warning to the end user/ build to aid problem diagnosis.

Expected

If NXRM encounters an end-user relevant problem(s) fulfilling a NuGet v3 request, then the NXRM response should include this header(s) with an end user appropriate message(s).