Look for apt-verify/verify.d in /etc, /usr/local/share, /usr/share
Use a search path, where programs in earlier directories override those with identical basenames in later ones. This allows the sysadmin to install their own programs to override packaged ones, without any use of dpkg-divert or maintainer scripts.
Update all the documentation accordingly.
Remove the README from the verify.d directory, as the user is more
likely to find the documentation in the apt-verify(8) manpage or in
/usr/share/doc/apt-verify. This avoids requiring
/etc/apt-verify/verify.d to exist just for the README. Having a README
in that directory seems less critical now that that directory no longer
contains symlinks (and in a normal installation will contain nothing at
all).
The Debian packaging can now install the gpgv symlink into
/usr/share/apt-verify/verify.d.