Fix http -> https redirects

[timbod7]

The code will current generate a proxy config like:

  server {
    listen 80;
    server_name app.powerlinespro.com app.prod.powerlinespro.com api.prod.powerlinespro.com app.powerlinespro.co;
    location '/.well-known/acme-challenge' {
        default_type "text/plain";
        alias /opt/var/www/.well-known/acme-challenge;
    }
    location / {
      return 301 https://$server_name$request_uri;
    }
  }

But this always redirects to the first server name as per here:

https://serverfault.com/questions/706438/what-is-the-difference-between-nginx-variables-host-http-host-and-server-na

Looks like we need to change $server_name to $host

[timbod7]

here:

https://github.com/helix-collective/camus2/blob/master/config/nginx.conf.tpl#L75