This ensures that when the operation to install the app completes, the
app is ready to run — rather than having to wait for subsequent
operations to install extensions which the app depends on (such as
content, or locales).
This fits in with the current ordering for *un*installing apps, where
the main app is uninstalled first, followed by its extensions.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
https://github.com/flatpak/flatpak/issues/3017