how can i add the partner table fields to be shown on user registration page? i know there's a phone number field on res_partner, but not on res_user table. and also i believe the data is saved on the res_partner table once the user sign up. 

i only find the end of user sign up model which is in : auth_signup/models/res_users.py/_create_user_from_template

    def _create_user_from_template(self, values):
        template_user_id = literal_eval(self.env['ir.config_parameter'].sudo().get_param('base.template_portal_user_id', 'False'))
        template_user = self.browse(template_user_id)
        if not template_user.exists():
            raise ValueError(_('Signup: invalid template user'))

        if not values.get('login'):
            raise ValueError(_('Signup: no login given for new user'))
        if not values.get('partner_id') and not values.get('name'):
            raise ValueError(_('Signup: no name or partner given for new user'))

        # create a copy of the template user (attached to a specific partner_id if given)
        values['active'] = True
        try:
            with self.env.cr.savepoint():
                return template_user.with_context(no_reset_password=True).copy(values)
        except Exception as e:
            # copy may failed if asked login is not available.
            raise SignupError(ustr(e))

what I've tried: create similar fields on res_user, and it is successfully saved on res_user, but not saved on res_partner field.