/**
  * @param array $uploadIds
  *
  * @return string
  */
 public function generateAccessToken(array $uploadIds)
 {
     $token = md5(uniqid());
     Upload::whereIn('id', $uploadIds)->update(['access_token' => $token, 'access_token_expiration' => time() + 1800]);
     return $token;
 }