Draft: Fix/rapid cdn assure http1.1 websocket client origin

When websocket is used it shall be assured that CDN will only use HTTP/1.1 from the client and to the backend, as this will lead to problems. The CDN shall assure such scenario, even if the cluster or slave is using other protocol versions (especially HTTP/2 or HTTP/3).

Also websocket have to be fully tested on the full chain, from the client to the origin, including cached slaves.

Backend needs to be at least like https://echo.websocket.org/ , the client shall be recurls, with eventual improvements to allow it play with websocket directly to make assertions.

Inspire from https://websockets.readthedocs.io/en/stable/