This adds new FlatpakTransaction API, and a new top level CLI command to
preinstall flatpaks, that is to install flatpaks that are considered
part of the operating system.
A new drop-in directory /etc/flatpak/preinstall.d/ allows configuring
what apps should be preinstalled, and a new flatpak preinstall command
installs and removes apps based on the current configuration.
A drop-in loupe.preinstall file can look something like this:
[Flatpak Preinstall org.gnome.Loupe]
Branch=stable
IsRuntime=false
The corresponding API is flatpak_transaction_add_sync_preinstalled()
which can be implemented by GUI clients to drive the actual installs
on system startup.
Resolves: https://github.com/flatpak/flatpak/issues/5579
Co-authored-by: Sebastian Wick <sebastian.wick@redhat.com>
