implement ifwait trigger service and use in bridge

should we convert all ifwait uses to this trigger too? seems
reasonable

modules/bridge/members.nix

@@ -2,6 +2,7 @@
   liminix
 , ifwait
 , lib
+, svc
 }:
 { members, primary } :
 
@@ -10,14 +11,20 @@ let
   inherit (liminix.services) bundle oneshot;
   inherit (lib) mkOption types;
   addif = member :
-    oneshot {
-      name = "${primary.name}.member.${member.name}";
-      up = ''
-        dev=$(output ${member} ifname)
-        ${ifwait}/bin/ifwait $dev running && ip link set dev $dev master $(output ${primary} ifname)
-      '';
-      down = "ip link set dev $(output ${member} ifname) nomaster";
+    # how do we get sight of services from here? maybe we need to
+    # implement ifwait as a regualr derivation instead of a
+    # servicedefinition
+    svc.ifwait.build {
+      state = "running";
+      interface = member;
       dependencies = [ primary member ];
+      service = oneshot {
+        name = "${primary.name}.member.${member.name}";
+        up = ''
+          ip link set dev $(output ${member} ifname) master $(output ${primary} ifname)
+        '';
+        down = "ip link set dev $(output ${member} ifname) nomaster";
+      };
     };
 in bundle {
   name = "${primary.name}.members";