freeradius: fix radius user

We now must choose either system or normal user when creating a user

nixos/modules/services/networking/freeradius.nix

@@ -28,6 +28,7 @@ let
         ProtectHome = "on";
         Restart = "on-failure";
         RestartSec = 2;
+        LogsDirectory = "radius";
     };
   };
 
@@ -73,6 +74,7 @@ in
       users.radius = {
         /*uid = config.ids.uids.radius;*/
         description = "Radius daemon user";
+        isSystemUser = true;
       };
     };