Function getOriginURL
Parameters
- req: SupportedRequestSubset
Request object
- pathname: string
Local path as specified by app. Browsers should pass
location.pathname. The URL may or may not start with a slash but may not be a full url.
Returns null | string
The pathname rebased to the actual origin URL or null if we couldn't safely determine it
- req: SupportedRequestSubset
Reconstruct the client's URL based on a pathname and unforgable headers (Origin or Referer) and on requesturl otherwise (if it's not a browser invoking us)