The unit that will copy authelia's minted OIDC client secrets into the store
needs an identity of its own. Not the controller's: that grant includes
rewriting every hive's policy and login role, which a unit whose whole job is
copying one file has no business holding.
The subject joins `certAuthCns`, so it is unrepresentable as a hive name for
the same reason the controller's is — cert auth trusts the CA, and a hive's
own leaf carries its name as the CN.
The module-eval case collides with the SECOND list element and leaves the
controller's subject at its default. A list with one consulted element and one
dead one is indistinguishable from the first element's case, so without this
the addition could be inert and nothing would say so.
Refs #3853
e8ff633c6b