This commit introduces a "_is_portal" method complementary to the existing "_is_internal" and "_is_public". The goal is to ease usage through the code base and be able to easily distinguish our 3 main use cases: public, portal and internal users. Task-3056280 closes odoo/odoo#120827 Related: odoo/enterprise#38575 Related: odoo/upgrade#4575 Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>