Extract shared DNS checks into dnsclient and fail closed on
truncated or non-success CAA responses. Climb past eTLD+1,
validate RFC 8659 issue-value syntax, and map NXDOMAIN TXT
lookups to the pending-verification path.
Signed-off-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: Bryan FRIMIN <bryan@frimin.fr>
