In the 1:3.19-1 a bunch of optional modules are installed as
`/lib/<triplet>/libmu_*.so.9.0.0`.  Most/all of these are unused in
some/many installations.

Could these be split into individual per-module packages and have the
main package recommend instead of depending?  I note `libmu_auth.so.9.0.0`
accounts for most of the mailutils dependencies (*both* MariaDB and
PostgreSQL), yet this isn't required in all installations.

If there are additional modules not available by default, perhaps those
could also get packages?

This would also resolve #253115.