Purpose
=======
Add a unicity constraint (on the url, UTM campaign, medium and source).
As we must care about null values, we can not implement it in SQL
(possible in pure SQL, but we will need to create an index on the
columns, which is not possible in Odoo if we want to customize the
error message).
Clean the code, before the "search or create" behavior was implemented
in the create, causing strange behavior (creating a link tracker with
the same values as an existing one didn't raise an error, but open
the form view of the existing link tracker).
Task-2090344
closesodoo/odoo#48845
Related: odoo/enterprise#9608
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>
std-odoo
b7e5eb639a