Improved fingerprint handling

[samcday]

Do something nicer when greetd gives us the "waiting for fingerprint" info message.

[samcday]

Do fprint messages just show on the session bus somewhere?

If so, could write a simple listener that shows a fingerprint icon in the top bar when fingerprint verification is in progress.

[samcday]

I followed this up further upstream as well: https://gitlab.gnome.org/World/Phosh/phosh/-/issues/1070

I think the visual improvements could be interesting to prototype in phrog, and if they come out nicely maybe it is something that could head upstream and find utility elsewhere. We'll see.

I do think that the best approach to handling the fingerprint UX through greetd conversation is by using extra signalling from the fprint dbus interface. If a signal that a fingerprint scan took place is seen, we can progress the conversation at that point.

[samcday]

This depends on #37

[samcday]

3b9456d improves things a bit already, I had some silly code to delay the greetd responses to info/error messages by 1 second. Sending the response immediately makes the fingerprint auth flow quite snappy.

The visual UX improvements detailed in the upstream ticket are still worthwhile.

[samcday]

Tentatively aiming this at 0.43.0. For now, the recent commit makes things quite usable.