title: Difference between GATEWAY_REQUEST_URL_ATTR and request URI
body: <p>What is the difference between <code>GATEWAY_REQUEST_URL_ATTR</code> and request URI from <code>ServerWebExchange</code>? In some built-in filters like <code>ForwardPathFilter</code> only the URI of the request is modified but in others e.g. <code>RewritePathGatewayFilterFactory</code>, they are both changed. When creating a custom filter for changing something in the URL should I change one of these or both?</p>