Copy cookies in RenderingResponse.from() - #37378

Overivew

RenderingResponse.from() does not copy the cookies of the given response, unlike ServerResponse.from(). As a result, a HandlerFilterFunction that rebuilds a rendering response to add a shared model attribute drops cookies set by the handler.

For example, in WebMvc.fn:

HandlerFilterFunction<RenderingResponse, RenderingResponse> filter =
        HandlerFilterFunction.ofResponseProcessor((request, response) ->
                RenderingResponse.from(response)
                        .modelAttribute("currentPath", request.path())
                        .build());

If the handler sets a cookie to store a user preference, this filter drops the cookie from the response, so the updated preference is not remembered on subsequent requests.

This PR updates RenderingResponse.from() to copy cookies in both WebMvc.fn and WebFlux.fn, matching the behavior of ServerResponse.from().

Related Issues

• WebFlux ServerResponse built from other ServerResponse drops cookies and hints #22481