A few failures in the automatic tests
Nonexistant environment variable HOME
Indeed, it works for me because I set HOME in the systemd configuration file:
% grep Environ /etc/systemd/system/multi-user.target.wants/icinga2.service
EnvironmentFile=/usr/lib/icinga2/ic…
Obey the IANA caching
RFC 9111, section 4.2.1 is clear: use Cache-Control: max-age
(today, both headers give exactly the same result).