A root-only link inside /var/lib/mesh pointing out of it would have made a
directory outside the tree, owned by the engine's account, the mesh's to give
away: the fault of issue 1873 again. The path and the tree's root are now both
resolved, links followed, and the directory is the tree's only when the resolved
path lies below the resolved root as well.
postgres's data directory moved to /var/lib/mesh/postgres. On ace and novox that
directory was there, root:root 0700, before the directory resource was applied, so
the engine used it as found (issue 339's rule) and left it to root: the postgres
provider, running as the operator's account, cannot reach its own secrets,
consumers and grants there.
/var/lib/mesh is the engine's tree (root, 0755): only the engine's account makes a
directory in it. A directory below it owned by that account is now the mesh's and
is given its declared owner and mode. Anywhere else, or owned by another account,
issue 339's rule stands.