Implement NetworkManager secrets
For Network Manager to ask for Network passwords, there should be an implementation of NMSecretAgentOld
registered. In GNOME, it's implemented in gnome-shell, where the backend is written in C[0][1] and the UI in javascript[2].
As Wifi shall be managed by the main UI too, the best place to have such an implementation would be phosh, which can also used by apps like gnome-control-center. We may make use of gcr library to create system wide dialogs.
[0] https://gitlab.gnome.org/GNOME/gnome-shell/blob/master/src/shell-network-agent.c
[1] https://gitlab.gnome.org/GNOME/gnome-shell/blob/master/src/shell-network-agent.h
[2] https://gitlab.gnome.org/GNOME/gnome-shell/blob/master/js/ui/components/networkAgent.js