Add haproxy.debian.net repository
I say "haproxy.debian.net" since the repository is not officially maintained by HAProxy people. However, we have their blessings, so maybe the description should just be "HAProxy repository".
Also, the suite names do not match the official Debian suite names. From your blogpost, it seems extrepo doesn't expect the user to specify a suite name. I could create different section for each version (
haproxy-1.9, ...) and use
Suites: <SUITE>-backports-2.0. Would it be better? If yes, to avoid duplication of many stuff, are we allowed to use YAML anchors?