ISC DHCP client/relay end of maintenance

https://lists.isc.org/pipermail/dhcp-users/2021-June/022495.html

ISC would like to end maintenance of the ISC DHCP *client and relay* by the
end of 2021.  We plan to continue maintaining the DHCP *server*, and any
code that is common between the server, client and relay for a couple more
years at least.  Our January 2020 release of ISC DHCP incorporated a number
of submitted patches, mostly for the client, but otherwise we have done
little maintenance on the client or relay.  To be honest, the client and
relay have simply not been a focus of ours for several years.  As a small
non-profit organization, we have to allocate our limited resources carefully
and we think the ISC DHCP server, and Kea have more future value for users.