Add support for hostnames in configuration files
Currently, as stated in https://lists.isc.org/pipermail/kea-users/2021-December/003287.html, Kea does not support hostnames in configuration files. With kubernetes in mind, where IP addresses are highly short-lived, supporting hostnames can be a major improvement.
Note that ISC DHCP server does support hostname in configs (https://kb.isc.org/v1/docs/isc-dhcp-44-manual-pages-dhcpdconf#configuring-failover), so some implementation concepts could be borrowed from there.