Purpose
=======
When a user receives an email to activate their account, allow them to
click on the "Activate Account" button after the account has already
been activated instead of showing a "Invalid signup token" error.
Specifications
=============
Add a parameter p_id to the sign up url to check if the partner has
already activated their account (if their user_ids state is not new) and
redirect them to login otherwise.
Task-2680414
closesodoo/odoo#79936
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>