$userId = '12345';
$claims = [
'iss' => $config->boxAppSettings->clientID,
'sub' => $userId,
'box_sub_type' => 'user',
'aud' => $authenticationUrl,
'jti' => base64_encode(random_bytes(64)),
'exp' => time() + 45,
'kid' => $config->boxAppSettings->appAuth->publicKeyID
];