[FIX] auth_signup: Error when sending quotation

Fine tuning of this commit:odoo@7501691
Fields signup_token, signup_type, signup_expiration are protected
When sending a quotation (mail template 'Sales Order - Send by Email'):
the token needs to be read (and sometimes written)

opw:1907157

addons/auth_signup/models/res_partner.py

@@ -59,17 +59,17 @@ def _get_signup_url_for_action(self, action=None, view_type=None, menu_id=None,
         for partner in self:
             # when required, make sure the partner has a valid signup token
             if self.env.context.get('signup_valid') and not partner.user_ids:
-                partner.signup_prepare()
+                partner.sudo().signup_prepare()
 
             route = 'login'
             # the parameters to encode for the query
             query = dict(db=self.env.cr.dbname)
-            signup_type = self.env.context.get('signup_force_type_in_url', partner.signup_type or '')
+            signup_type = self.env.context.get('signup_force_type_in_url', partner.sudo().signup_type or '')
             if signup_type:
                 route = 'reset_password' if signup_type == 'reset' else signup_type
 
-            if partner.signup_token and signup_type:
-                query['token'] = partner.signup_token
+            if partner.sudo().signup_token and signup_type:
+                query['token'] = partner.sudo().signup_token
             elif partner.user_ids:
                 query['login'] = partner.user_ids[0].login
             else: