Supporting unbound in stretch by upgrading to 1.9

[Sylvain Beucler <beuc@beuc.net>]

Hi Security Team,

The LTS project would like to keep supporting 'unbound', for which 
security support was dropped last May (DSA 4694-1), IIRC due to the 
risks of maintaining a version that was not supported upstream anymore.

The plan we identified is to backport buster's versions 
(1.9.0-2+deb10uX), along with rebuilding 3 reverse dependencies 
(getdns/gnutls28/opendkim) to use the newer libunbound8, which appears 
backward-compatible. The version scheme could be 1.9.0-2+deb10uX~deb9uY.

Would you be OK with this plan?

(Adding maintainer Robert Edmonds in Cc: as well, in case we missed a 
blocking issue.)

Cheers!
Sylvain Beucler
Debian LTS Team