[IMP] account: email notification button for all users

The access/follow/actions buttons on the notification email template
are sent only to employee. For this particular business model when
want all the users to receive them, as the portal users.

addons/account/models/account_invoice.py

@@ -987,6 +987,18 @@ class AccountInvoice(models.Model):
         res = map(lambda l: (l[0].name, formatLang(self.env, l[1], currency_obj=currency)), res)
         return res
 
+    @api.multi
+    def _notification_group_recipients(self, message, recipients, done_ids, group_data):
+        group_user = self.env.res('base.group_user')
+        for recipient in recipients:
+            if recipient.id in done_ids:
+                continue
+            if not recipient.user_ids:
+                group_data['partner'] |= recipient
+            else:
+                group_data['user'] |= recipient
+            done_ids.add(recipient.id)
+        return super(AccountInvoice, self)._notification_group_recipients(message, recipients, done_ids, group_data)
 
 class AccountInvoiceLine(models.Model):
     _name = "account.invoice.line"