Add more users to the project.

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

def prj_add_user(self, *args, **kwargs):
        """Add more users to the project.

        :returns: None
        :rtype: None
        :raises: None
        """
        if not self.cur_prj:
            return
        dialog = UserAdderDialog(project=self.cur_prj)
        dialog.exec_()
        users = dialog.users
        for user in users:
            userdata = djitemdata.UserItemData(user)
            treemodel.TreeItem(userdata, self.prj_user_model.root)
        self.cur_prj.save()