Parsed GMS join response

        $info = curl_getinfo($conn);

        if ($info['http_code'] === 200) {

            error_log($response);

            $joinResult = json_decode($response);

            curl_close($conn);

            if (!array_key_exists('mergedId', $joinResult)) {

                throw new ServerErrorException('GMS join response has an invalid payload');

            }

            return $joinResult->mergedId;

        } else {

            //show information regarding the error

            curl_close($conn);

            }

            throw new ServerErrorException('Error: GMS response code: ' . $httpCode);

        }

        // TODO: return id extracted from GMS response

        return $userId1;

    }

    private function getJoinAccessToken(int $userId1, int $userId2): string {