nixos/murmur: add murmur group, don't run as nogroup

fixes #101980

nixos/modules/misc/ids.nix

@@ -468,7 +468,7 @@ in
       #minecraft = 114; # unused
       vault = 115;
       #ripped = 116; # unused
-      #murmur = 117; # unused
+      murmur = 117;
       foundationdb = 118;
       newrelic = 119;
       starbound = 120;

nixos/modules/services/networking/murmur.nix

@@ -278,6 +278,10 @@ in
       home            = "/var/lib/murmur";
       createHome      = true;
       uid             = config.ids.uids.murmur;
+      group           = "murmur";
+    };
+    users.groups.murmur = {
+      gid             = config.ids.gids.murmur;
     };
 
     systemd.services.murmur = {
@@ -300,6 +304,7 @@ in
         RuntimeDirectory = "murmur";
         RuntimeDirectoryMode = "0700";
         User = "murmur";
+        Group = "murmur";
       };
     };
   };