The whole purpose of this module was to be able to separate a customer and a supplier portals.
Given the status of the upstream implementations of portals, it is not possible to have a supplier portal without portal permissions. Thus, it would be required to make the group this module was creating inherit from `base.group_portal`, which would give suppliers access to all customers portal. As such, that group becomes useless.
From now on, this distinction should be made with simply checking if `user.customer` or `user.supplier` is `True`. This means no additional problems since `ir.rule` domains can use the `user` variable. To allow that, I'm implementing what was discussed at https://github.com/OCA/server-tools/pull/434#discussion-diff-64883758.
Tests had to be removed because https://github.com/odoo/odoo/issues/12237 makes the created record to disappear, so there's no way to actually check the created user was created with customer or supplier flag on.
Jairo Llopis