[FIX] web_settings_dashboard: token when inviting users

A context key was missing, leading to incorrect token sent to users when adding
users through the settings dashboard.

Also removed unused imports.

addons/web_settings_dashboard/models/res_users.py

@@ -1,10 +1,6 @@
 # -*- coding: utf-8 -*-
 
-from datetime import datetime, timedelta
-
-from openerp import models, api, _
-from openerp.exceptions import RedirectWarning
-from openerp.tools.misc import DEFAULT_SERVER_DATETIME_FORMAT
+from openerp import models, api
 
 
 class Users(models.Model):
@@ -23,6 +19,6 @@ class Users(models.Model):
         # Process new email addresses : create new users
         for email in new_emails:
             default_values = {'login': email, 'name': email.split('@')[0], 'email': email, 'active': True}
-            user = self.create(default_values)
+            user = self.with_context(signup_valid=True).create(default_values)
 
         return True