public static function signin($options)
 {
     $CI =& get_instance();
     $CI->load->library("JWT");
     $CI->load->model('user_model');
     $results = $CI->user_model->getByUsernameAndPassword($options);
     $return = array();
     if (!empty($results)) {
         $user = CI_User::getInstance($results[0]);
         $token = $CI->jwt->encode(array('userId' => $user->getId(), 'issuedAt' => time(), 'ttl' => time() + TOKEN_TTL), SECRET);
         $return = array('user' => $user, 'token' => $token);
     }
     return $return;
 }