Easy!Appointments has server-side request forgery in CalDAV connection test that exposes the deployment's internal network

Easy!Appointments is a self hosted appointment scheduler. In versions prior to 1.6.0, `Caldav::connect_to_server` at `application/controllers/Caldav.php:60` hands the request's `caldav_url` to a Guzzle `REPORT` call without scheme or host validation. A logged-in backend user (admin, provider, or secretary) reaches loopback, RFC1918, and link-local hosts on the deployment's network. The Guzzle exception path returns the upstream status code plus ~120 bytes of response body in the JSON `message` field (`Caldav.php:74-78`), so the SSRF is semi-blind. Version 1.6.0 contains a patch.