sshguard: service creates /var/lib/sshguard

nixos/modules/services/security/sshguard.nix

···
             ReadOnlyDirectories = "/";
             ReadWriteDirectories = "/run/sshguard /var/lib/sshguard";
             RuntimeDirectory = "sshguard";
+            StateDirectory = "sshguard";
             CapabilityBoundingSet = "CAP_NET_ADMIN CAP_NET_RAW";
          };
       };