Multiple has_many :through

simplifying I’ve this:

user -> membership -> group -> grant -> right
user has_many group through membership and group has_many right
through grant.
I can fetch the groups’ rights well, doing some console stuff like
@user.groups.each do |group| ;; group.rights.each do |right| ;; puts ;; end ;; end etc.
it would be very powerful to be able to do @user.rights directly
with :uniq instead of querying groups’ rights, anybody can think of an
association like this?