When the app is properly launched, D-Bus activation will be followed
by a call to org.freedesktop.Application.Activate() to open the window.
But it's also possible for D-Bus activation to happen in other
circumstances, for example during gdbus command line completion.
We don't want to pop up a window then, so pass the --gapplication-service
flag to properly separate D-Bus activation from activating the app.
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2076>
Predefined categories aren't a great way for organizing installed
applications, but they have their use in "stores" like Software
or flathub.
Not listing any category means we fall through the cracks, so
pick the (hopefully) least inappropriate one ...
https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1160
The Extensions app code is now independent enough from the rest of the code
base to move it to its own subprojects, like we did for the extensions-tool.
This allows for stand-alone builds of the app, which we are about to use
for distributing it as flatpak.
https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1133