plugin download: use cache if dest_path is empty: if dest_path is not set, the file will be downloaded in cache. A new name will be generated using a hash of the uri. If the file is already downloded in cache, it won't be downloaded again (in this case returned progress_id is an empty string).

You'll find install instructions in documentation (see doc/installation.rst).

If you need help, come the SàT official XMPP room: sat@chat.jabberfr.org or join us with a web browser via https://chat.jabberfr.org/converse.js/sat@chat.jabberfr.org