fix: use X-Forwarded-Uri if it exists for pathRegex match

the functions `isApiPath` and `isAllowedPath` use the `req.URL.Path` property which leads to faulty behavior when behind a reverse proxy. The correct path can be inferred from the `X-Forwarded-Uri` header by making use of the already provided `requestutil.GetRequestURI` function.

Co-authored-by: Jan Wystub <jan@bam-bam-bam.com>