This role manages all hostnames of the target server,
both /etc/hostname and additional hostnames in
/etc/hosts.
At the bare minimum, you need to specify hostname_fqdn,
this is the primary hostname of the target, which ends up
in /etc/hostname.
You can specify additional hostnames for /etc/hosts in
hostname_extra_hosts in the form of {ip, fqdn, alias[] },
following conventions usual for /etc/hosts (single IP,
FQDN first and aliases as plain hostnames).
This role uses the hostnamectl command installed by
default on debian-like distros in order to ensure the
new hostname is immediately set without needing to reboot.