RFC: roles

I had a look at roles, and was wondering about the best way to support them.

Purely, it's not a problem at all: just expose pg_authid and
pg_auth_members in dialogs/lists.

OTOH, it might be quite confusing for 1st time users that there are only
roles with some attributes, no users and groups. Should we have two
modes for it: The reduced view with users and groups (where a group may
be a group member too) and an enhanced view that allows all role features?
Additionally, this has also some impact on the security properties,
since a role that may login currently wouldn't be exposed as grantee by
default.

Thoughts?

Regards,
Andreas