def has_many_through_identity(assoc, options={})
      fk = :"#{model_name.to_s.underscore}_identity"
      pk = IDENTITY_COLUMN

      has_many assoc, {:foreign_key=>fk, :primary_key=>pk}.merge(options)
    end
def has_many_through_identity(assoc, options={})
      fk = :"#{model_name.to_s.underscore}_identity"
      pk = IDENTITY_COLUMN

      has_many assoc, {:foreign_key=>fk, :primary_key=>pk}.merge(options)
    end
Association to be used in a parent class which has identity and has children
 which don't have identities;
 the association is implemented through the identity, not the PK.
 The inverse association should be belongs_to_identity