Add support for reading launch flags from a config file

[guihkx]

This is a question for maintainers on how they feel about support reading launch flags (a.k.a. command-line arguments) from a config file, similarly to how it was done on the Spotify package:

• https://github.com/flathub/com.spotify.Client/pull/264

This would be a useful feature for me personally, as I want to invoke Discord with --password-store=basic to silence these (harmless) error messages coming from Chromium:

$ flatpak run com.discordapp.Discord
[...]
[5:0518/154935.625234:ERROR:object_proxy.cc(577)] Failed to call method: org.kde.KWallet.isEnabled: object_path= /modules/kwalletd6: org.freedesktop.DBus.Error.NoReply: Remote peer disconnected
[5:0518/154935.625267:ERROR:kwallet_dbus.cc(112)] Error contacting kwalletd6 (isEnabled)
[5:0518/154935.625543:ERROR:object_proxy.cc(577)] Failed to call method: org.kde.KLauncher.start_service_by_desktop_name: object_path= /KLauncher: org.freedesktop.DBus.Error.ServiceUnknown: The name is not activatable
[5:0518/154935.625561:ERROR:kwallet_dbus.cc(81)] Error contacting klauncher to start kwalletd6
[5:0518/154935.992836:ERROR:object_proxy.cc(577)] Failed to call method: org.kde.KWallet.close: object_path= /modules/kwalletd6: org.freedesktop.DBus.Error.NoReply: Remote peer disconnected
[5:0518/154935.992861:ERROR:kwallet_dbus.cc(503)] Error contacting kwalletd6 (close)
[...]

If maintainers don't oppose this, I could work on a pull request.

Thanks.

[guihkx]

Oh, wow. I messed up badly.

I meant to open this issue on the Discord tracker, not here.

My apologies.