Offer custom downloads in GNOME Boxes

[Felipe Borges <felipeborges gnome org>]

Hi,

If you are distributing GNOME Boxes, you probably already seen that
for the past couple of versions we have a "Download an OS" page in the
new machine assistant which is a nice shortcut to obtain an ISO and
setup a virtual machine[0].

The list is powered by libosinfo's osinfo-db[1], which is a database
of operating systems data, including URLs for medias (for those freely
available). Boxes has a "recommended" section which presents manually
curated entries, and this list can now be customized by distributors.

All in all, if you want to promote the download of certain OSes in
that page, you just need to tweak an XML file
(recommended_downloads.xml)[1]. It is a simple list of Osinfo IDs
which can be sorted as desired.

Make sure the OSes listed there are in the osinfo-db package which you
are distributing. the osinfo-db module can always be safely rebased to
its latest release, it contains only XML files describing OSes and
devices. We plan to land soon an API which will enable Boxes (and
other clients) to programmatically update the database.

[0] https://feborg.es/boxes-downloadable-oses/
[1] https://gitlab.com/libosinfo/osinfo-db
[2] https://gitlab.gnome.org/GNOME/gnome-boxes/blob/master/data/recommended-downloads.xml