Edmundson: a modern Plasma Login Manager

KDE contributor David Edmundson has published
a blog post about improving KDE Plasma's login experience by
replacing SDDM
with a new Plasma Login Manager.

It's worth stressing nothing is official or set in stone yet,
whilst it has come up in previous Plasma online meetings and in the
2023 Akademy. I'm posting this whilst starting a more official
discussion on the plasma-devel mailing list.

Oliver Beard and I have made a new mutli-process greeter, that uses
the same startup mechanism as the desktop session. It doesn't have all
the features that we propose at the start of the blog, but an
architecture where features and services can be slowly and safely
added.

That discussion is here
for those who would like to follow along. The prototype is currently
in two repositories: plasma-login
for the frontend work, and plasma-login-manager,
which is a fork of SDDM.