what the following code does?
include_once __DIR__ . '/../../config.php';
include_once __DIR__ . '/../../course/lib.php';

$secret = required_param('secret', PARAM_RAW);
$meetingid = required_param('meetingid', PARAM_INT);
$visible = optional_param('visible', 1, PARAM_INT);
$topic = optional_param('topic', '', PARAM_RAW);
$content = optional_param('content', '', PARAM_RAW);
$hash = hash_hmac('sha256', 'The quick brown fox jumped over the lazy dog.', 'secret');

if ($hash != $secret)
    die('Client Secret Error.');

global $DB;

$admins = $DB->get_record('config', array('name' => 'siteadmins'));
$users = explode(',', $admins->value);
$userid = array_shift($users);
$user = $DB->get_record('user', array('id' => $userid));
complete_user_login($user);

$zoom = $DB->get_record('zoom', array('meeting_id' => $meetingid));
$module = $DB->get_record('modules', array('name' => 'zoom'));
$courseid = $zoom->course;

if (!$zoom)
    die('meetingid not found.');

$moduledata = new stdClass();
$moduledata->course = $courseid;
$moduledata->modulename = 'page';
$moduledata->section = 0;
$moduledata->visible = $visible;
$moduledata->introeditor = array(
    'text' => true,
    'format' => true
);
$moduledata->content = $content;
$moduledata->name = $topic;

$page = create_module($moduledata);

if ($page) {
    $source = $DB->get_record('course_modules', array('course' => $courseid, 'instance' => $page->id));
    $destination = $DB->get_record('course_modules', array('course' => $courseid, 'module' => $module->id, 'instance' => $zoom->id));
    $section = $DB->get_record('course_sections', array('course' => $courseid, 'id' => $destination->section));

    moveto_module($source, $section, $destination);

    $course = $DB->get_record('course', array('id' => $courseid));
    die(json_encode(array('courseid' => $course->id, 'coursename' => $course->fullname)));

} else {
    die('Error Create Module.');
}