On some LDAP servers, the `uid` attribute is more like a guid, while the
username exists instead in a dedicated field, like `username`. This
means the `uid` is not necessarily equal to `username`.
This is allows referencing using the `uid` to search for groups in the same
way as `dn` so that one can explicitly match the `memberuid` to the `uid` for
the user without the assumptions that come with using `{0}`.