has_many + habtm on same model

Hello,

In a situation where a user has_many :groups (it owns the group) but also has_and_belongs_to_many :groups, how is this most easily represented?

The only way i have found is

user.rb:
has_many :groups

has_and_belongs_to_many :memberships, ,:join_table => ‘memberships’, :class => ‘group’

group.rb
belongs_to :user
has_and_belongs_to_many :memberships, , :join_table => ‘memerships’, :class => ‘user’

I think there is an opportunity to have a new model membership.rb that belongs_to :user, belongs_to :group where a user has_many :groups, :through => :membership but not 100% sure.

What is the cleanest approach here?

Adam