Protocol (De)capsulation

[XAMPPRocky]

Reading this Cloudflare proxy framework announcement, the concept of protocol capsulation and decapsulation, is a compelling concept for having Quilkin more flexible and compatible with future protocols like QUIC and allow Quilkin to operate at lower layers such as ICMP.

This would have several benefits on multiple levels, having ICMP support would allow Quilkin to listen at lower level on the edge, and support for QUIC would allow for support for HTTP/3 which opens the door for more standard ways of adding metadata information through headers which would be more standard and wouldn't require custom protocol data units like UDP does.

These are more a future concern than a something Quilkin needs right now though, as currently UDP is the most flexible in terms of platform support for both clients (compared to QUIC/HTTP3) and proxies on the cloud provider side (not everything allows for ICMP access since it requires kernel privileges). But I think this will become a key feature for Quilkin to allow for better and more standard behaviour for the future.