[FIX] auth_signup: add missing dependency on the computation of the signup validity

The field signup_valid is a non stored computed field based on signup_token.
The cache is filled with prefetched values, so in a loop the field is read from
the cache and not recomputed due to the missing dependency.

opw 1843442

addons/auth_signup/models/res_partner.py

@@ -33,6 +33,7 @@ class ResPartner(models.Model):
     signup_url = fields.Char(compute='_compute_signup_url', string='Signup URL')
 
     @api.multi
+    @api.depends('signup_token', 'signup_expiration')
     def _compute_signup_valid(self):
         dt = now()
         for partner in self: