fix: the web service manages users also when it started before setup.

ADR.md

@@ -143,8 +143,10 @@ Decision: `vpnrouter_users.py` holds the user operations, the checks and a sessi
 lock and the connection of the user manager account. The web service imports it and maps a
 `Failure` to the HTTP status; `vpn-router-user` imports it and adds the argument parsing and
 the output, text for people and JSON with `--json`. The web unit allows writing the paths the
-operations need: `/run/vpn-router` for the lock, `/etc/vpn-router/pki` for the certificates and
-the CA's state, and `/etc/swanctl/x509crl` for the published CRL.
+operations need: `/run/vpn-router` for the lock, its `RuntimeDirectory`, which systemd creates
+before the service starts, also before setup has run, and keeps when it stops, as setup's state
+files are there too; `/etc/vpn-router/pki` for the certificates and the CA's state, and
+`/etc/swanctl/x509crl` for the published CRL.
 
 Consequences: The rules exist once. A request starts no process, and a password never leaves
 the process that received it. The web service imports `python3-ldap` and the package's