protected HttpRequestMessage transformRequest(HttpRequestMessage requestMsg) {
        HttpRequestMessage massagedRequest = massageRequestURI(requestMsg);

        Headers headers = massagedRequest.getHeaders();
        REQUEST_HEADERS_TO_REMOVE.forEach(headerName -> headers.remove(headerName.getName()));

        addCustomRequestHeaders(headers);

        // Add X-Forwarded headers if not already there.
        ProxyUtils.addXForwardedHeaders(massagedRequest);

        return massagedRequest;
    }
Request is replayable on a different origin IFF
A) we have not started to send response back to the client  AND
B) we have not lost any of its body chunks
zuul-core/src/main/java/com/netflix/zuul/filters/endpoint/ProxyEndpoint.java