add bandwidth as a service option for ppp (l2tp, pppoe)

modules/ppp/common.nix

@@ -13,6 +13,7 @@
   username,
   password,
   lcpEcho,
+  bandwidth,
   ppp-options,
   dependencies ? [ ],
 }:
@@ -115,7 +116,7 @@ let
       ${command}
     '';
     notification-fd = 10;
-#    properties.bandwidth = 3 * 1000 * 1000;
+    properties.bandwidth = bandwidth;
     timeout-up =
       if lcpEcho.failure != null then (10 + lcpEcho.failure * lcpEcho.interval) * 1000 else 60 * 1000;
     inherit dependencies;