Please unblock package lowdown, a key package, through:
  bind9 -> libmaxminddb -> lowdown

[ Reason ]
lowdown is a Markdown to HTML/roff/LaTeX/etc. translator. A regression
was introduced at some point where the -Tman (manpage) output used a
roff macro that is not present in the "man" package but in the "ms"
package. I reported this upstream[1], and it was subsequently fixed[2].

This is a bookworm-targeted backport of that specific upstream commit,
that applies cleanly as-is.

1: https://github.com/kristapsdz/lowdown/issues/111
2: https://github.com/kristapsdz/lowdown/commit/02491bf4ae2a39df2dfed10382512449a5b3262f

[ Impact ]
The output difference is minor from a visual standpoint, e.g.
   OPTIONS
          -batch_size ______
  -              Maximum  number  of  entries to request per call to get-entries.
  -              You should not generally need to change this. Defaults to 1000.
  +            Maximum number of entries to request per call to get-entries.  You
  +            should not generally need to change this. Defaults to 1000.

However, the roff output is technically invalid.

In Debian, this manifests in reverse build-dependencies that are using
lowdown to generate their manpage to emit lintian warnings, e.g.:
    W: certspotter: groff-message 29: warning: macro 'PI' not defined [usr/share/man/man8/certspotter-script.8.gz:1]
    W: certspotter: groff-message 56: warning: macro 'PI' not defined [usr/share/man/man8/certspotter.8.gz:1]

There are three reverse build-dependencies in testing:
  1) src:libmaxminddb
  2) src:certspotter
  3) src:nix

Only the first two are using -Tman. I am the maintainer for both.
src:libmaxminddb was built with an pre-regression version of lowdown and
is not affected. It can be binNMUed, although not strictly necessary.

src:certspotter is affected and should probably be binNMUed, although as
explained, the visual impact is relatively minor.

[ Tests ]
Upstream has a comprehensive test suite that runs as part of the build.
The package also has autopkgtests that pass.

[ Risks ]
The code for the fix is trivial. The package is technically a key
package, but only as a reverse build-dep of another package, and is only
a B-D for three packages in total.

[ Checklist ]
  [x] all changes are documented in the d/changelog
  [x] I reviewed all changes and I approve them
  [x] attach debdiff against the package in testing

[ Other info ]
debdiff attached; you can also find the git diff at:
https://salsa.debian.org/debian/lowdown/-/commit/0e2160bb23e194edc5c15c7772042857fd18f2f7

unblock lowdown/1.0.0-2

Also probably:

nmu certspotter_0.16.0-1 . ANY . unstable . -m "Rebuild with lowdown 1.0.0-2"

(but no idea how to ensure the ordering of those two, not fluent in
wanna-build)

Unblocked.