explore different ways of combining nginx and php-fpm

[bpow]

• Nginx doesn't use env variables in its config files... So changing the upstream would require using HOSTALIASES or something. Or have a script to make the nginx default.conf from a template using env variables at startup... That would require that the place where default.conf goes be writable by whichever user runs it
• Maybe nginx should just be a completely different container/image (like nginxinc/nginx-unprivileged)? But then we'd still need access to the static files to be able to serve those-- so could mount as shared space, or just also copy those into that image, too...
• Right now, php-fpm is listening on a port, but could listen on a socket if it was in the same pod/container as nginx. That might involve using a sidecar in k8s or something like supervisord to run both nginx and php-fpm in the same container.