pub fn default_dir() -> PathBuf
The default per-user credential directory (RFC 0031 §11): $AGENTD_CRED_DIR, else $XDG_STATE_HOME/agentd/creds, else $HOME/.local/state/agentd/creds, else the OS temp dir.
$AGENTD_CRED_DIR
$XDG_STATE_HOME/agentd/creds
$HOME/.local/state/agentd/creds