Add setup instructions

[0xlua]

This repo is a flake and can be installed like one, however some actions have to be taken before doing so, mostly relating to file systems and secrets. I want to document these for future reference:

• Install NixOS with FDE¹ (see Full Disk Encryption, Secure Boot & Impermanence #126)
• enable secure boot: with sbctl create-keys and lanzaboote, also see Full Disk Encryption, Secure Boot & Impermanence #126
• generate an age key² and add it to .sops.yaml
• generate an ssh key³ and add it to authorizedKeys (also see ssh: use authorized keys file instead of hardcoded keys #201)
• obtain a PGP Key for Email encryption, add to stalwart and publish (also see Mail & Calendar clients #134)

Footnotes

1. Using the option in the NixOS Installer or disko ↩

2. preferably with something like age-plugin-yubikey or age-plugin-tpm ↩

3. preferably stored in TPM or YubiKey, also see Secret Management #127 ↩