log message that indicate successful configuration reload is needed
There is no log message that would say "ok, kea reconfigured successfully and it's ready to reply to traffic" after config reload. That would be helpful at least in automated testing.
something similar to kea start message:
INFO [kea-dhcp6.dhcp6/6239.140615276610048] DHCP6_STARTED Kea DHCPv6 server version 1.9.8-git started