feat: add default variables with explanation

Signed-off-by: Matej Focko <me@mfocko.xyz>

defaults/main.yml

@@ -0,0 +1,39 @@
+---
+# Username of the user that's being set up
+target_user: None
+
+# Group of the user that's being set up
+target_group: None
+
+# GitLab username used to obtain the public GPG key and public SSH keys
+gitlab_login: None
+
+# Full name for git
+fullname: None
+
+# Email used for git
+git_email: None
+
+# Signing key used for signing git commits and tags
+gpg_signingkey: None
+
+# Used as the FQDN that's set up in DNS and reachable from the network
+host_fqdn: None
+
+# Address of the HashiCorp Vault that is used to download the trusted CA
+# certificate for an SSH server setup
+hashicorp_vault_address: None
+
+# Address of the Vaultwarden instance
+vaultwarden_address: None
+
+# Used for Certbot and DDNS
+# Certbot: used for DNS verification of the domain during renewal
+# DDNS: used to update the DNS records of the public IP
+cloudflare_token: None
+
+# Cloudflare zone, the domain
+cloudflare_zone: None
+
+# Public ID tied to the Yubikey OTP
+yubikey_token_id: None