Referencing a header value in proxy

_From @kamil-mrzyglod on June 5, 2017 8:22_

Hi,

We're currently using Azure Functions Proxy in following scenario:

1. Client sends a request with a following header: **Authorization: TOKEN **
2. Proxy should rewrite a request from Authorization header to x-functions-key:

Is this possible with the current implementation of Proxy? I haven't found any way to do so and I don't know how it'd possible to reference to use it in the rewrite.

Any help is much appreciated.

Best regards,
Kamil

_Copied from original issue: Azure/azure-webjobs-sdk-script#1567_