Rewrite with nginx proxy_connect module

[mogul]

Bringing Caddy into the mix with a custom binary and using the binary buildpack makes this solution not a whole lot better than just building this custom CONNECT module and dynamically loading it into the NGINX buildpack. So we might think about adding a workflow to build the matching .so module file and simplifying the number of things folks have to understand about how this works by leaving Caddy out of the conversation. (More docs on how this module can be used.)

[mogul]

(Counterpoint: Programatically manipulating an nginx.conf file is pretty fragile, while Caddy can be configured with YAML and JSON. So Caddy may be a better option as we further abstract this into a broker.)