my $user = MyClass::DBI->do_transaction(sub {
    my($self) = @_;
    my $model = MyClass::DBI::Users->create({
        'user_id' => $self->user_id,
        'email_address' => $self->email_address,
    });
    foreach my $group ($self->groups) {
        $model->add_to_groups({ 'group_id' => $group });
    }
    return($model);
},$self);