/usr/bin/sabredav is in php-sabre-dav 1.8.12-3ubuntu2.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
1 2
#!/bin/sh php -S 0.0.0.0:8080 `dirname $0`/../share/php/Sabre/sabredav.php