public function changeRole($id, $user_id, $role)
{
$lrs = $this->show($id, []);
$lrs->users = array_map(function ($user) use($user_id, $role) {
$user['role'] = (string) $user['_id'] === $user_id ? $role : $user['role'];
return $user;
}, $lrs->users);
return $lrs->save();
}