Provide the alternatives to an appstream id together with the URL
This way we can count on the symmetry and don't reach cases like in the closed bug report where the flatpak id is not offered by the one coming from packagekit but not vice-versa.
This way we can count on the symmetry and don't reach cases like in the closed bug report where the flatpak id is not offered by the one coming from packagekit but not vice-versa.