Allow passing username and password through arguments

[Tiebe]

Is your feature request related to a problem? Please describe.
I'd like to integrate spotify-player into my NixOS config, including credentials. As of right now, anytime I reset my /home folder, or install on a new machine, I have to reauthenticate.

Describe the solution you'd like
It'd be awesome if there were a way to pass the username and password through the command line. I currently manage my secrets through sops-nix, and with an OneShot systemd service I would be able to authenticate anytime I rebuild NixOS.