automatic detector of common APT proxy settings

 auto-apt-proxy installs itself as an APT proxy autodetector, and detects
 common setups by checking localhost and the network default gateway for
 well-known APT proxies such as apt-cacher-ng.
 .
 This package is most useful for development environments, and will Do The
 Right Thing for:
 .
   * build chroots, with a proxy running on the host system.
   * docker/lxc containers, with a proxy running on the host system.
   * Virtual machines with NAT networking, with a proxy running on the host
   * system.
   * any other system, with a proxy running on its default gateway.
 .
 The following APT proxy servers are supported and automatically detected:
   * apt-cacher-ng
   * approx
   * apt-cacher
   * any proxy advertised by an _apt_proxy._tcp SRV record in your domain
 .
 This package has a minimal set of dependencies in order to minimize the
 influence on systems where it is installed.
 .
 This package does not query mDNS SRV records, which would require avahi.
 If you need that, consider the `squid-deb-proxy-client` package instead.