chore: copy readiness headers to the upstream request

When proxying the readiness request to the upstream function, we should
copy the original request headers. This allows the handler to use
headers, if needed. It also allows the of-watchdog to suppress the noisy
request logging for readiness checks.

Signed-off-by: Lucas Roesler <roesler.lucas@gmail.com>

main.go

@@ -414,6 +414,7 @@ func (r *readiness) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 			// we need to set the raw RequestURI for the function invoker to see our URL path,
 			// otherwise it will just route to `/`, typically this shouldn't be used or set
 			readyReq.RequestURI = r.endpoint
+			readyReq.Header = req.Header.Clone()
 			r.functionHandler.ServeHTTP(w, readyReq)
 			return
 		}