Nextcloud uses a _client-side_ (Javascript) redirect to navigate the
browser to its `index.php`. The page it serves with this redirect is
static and will often load successfully, even if there is a problem with
the application. This causes the Blackbox exporter to record the site
as "up," even when it it definitely is not. To avoid this, we can
scrape the `index.php` page explicitly, ensuring that the application is
loaded.