Use home-manager to create xsession.
Readme contains info on how to start xsession on login.
That way home-manager can maintain languages, keyboard and further stuff
globally for user.
No more need to set stuff as workaround within i3 or zsh.
Also enabled to start systemd units after login, as home-manager will
create and trigger `hm-graphical-session.target`.
The module doesn't work or exist anymore.
I use a lightwight battery icon instead which I add as a service to
start during login.
And I don't need the wifi thingy.
Do not hard code all values, instead configure them within home.nix.
This is more for learning purposes.
But port and allow might also be changed more frequently in general.
home-manager doesn't provide a systemd service itself.
That's why we build one ourself.
That also revealed a change in our directory structure.
The structure is now documented within readme.