Add users to the current task

        :returns: None
        :rtype: None
        :raises: None

def task_add_user(self, *args, **kwargs):
        """Add users to the current task

        :returns: None
        :rtype: None
        :raises: None
        """
        if not self.cur_task:
            return

        dialog = UserAdderDialog(task=self.cur_task)
        dialog.exec_()
        users = dialog.users
        for user in users:
            userdata = djitemdata.UserItemData(user)
            treemodel.TreeItem(userdata, self.task_user_model.root)