snapd-xdg-open is not using "io.snapcraft.*" namespace

[Conan-Kudo]

snapd-xdg-open offers a D-Bus interface on com.canonical.* namespace. While it's a perfectly valid namespace, it's very weird compared to the rest of the snap system, which uses the io.snapcraft.* namespace in various places.

Like everything else in the snap ecosystem, it should be using the io.snapcraft.* namespace.

[zyga]

I'm +1 on this. I think we need to have a grace period and listen on both but support only io.snapcraft.* with the next major release where we can assume people must rebuild their snaps.