Awareness of recent IETF ID and HAProxy Reverse HTTP support💡

**Describe the feature you'd like**

In July 2023, engineers from Meta and Nokia shared an Internet Draft describing a mechanism of origin server registration to an intermediate load balancer. The connection is established and then reversed, with traffic from the load balancer now flowing to the origin server. The typical use case is for automatic server discovery and registration, e.g. spinning up a k8s pod or a cloud instance and adding its private IP address to a load balancer so it can begin taking customer traffic. See https://datatracker.ietf.org/doc/draft-bt-httpbis-reverse-http/

Coincidentally, in HAProxy 2.9-dev4 release on August 25, 2023, a very similar feature was first introduced. See https://www.mail-archive.com/haproxy@formilux.org/msg43924.html

As both of these perform in some similar fashion to the Cloudflare Tunnel system, I think it would be great for you all to put heads together towards a future RFC that describes a vendor-interoperable specification. If nothing else, sharing Cloudflare's experience operating "Reverse HTTP" at scale would be very informative to the document authors. (There are substantial operational differences between Cloudflare Tunnel and in-the-same-datacenter load balancer-to-server registration tools, but still, pretty similar protocols and HTTP headers and all that jazz.)

Thanks!