refactor(registry): add stable uid registry

lib/default.nix

@@ -13,7 +13,6 @@ let
     mapAttrsToList
     ;
 
-  serviceIdentityRegistry = import ./service-identities.nix { inherit lib; };
   registry = import ./registry.nix { inherit lib self; };
 
   collectNixFiles =
@@ -90,6 +89,4 @@ in
 
   inherit (guests) deriveMac guest;
 
-  inherit (serviceIdentityRegistry) serviceUid;
-  serviceIdentities = serviceIdentityRegistry.identities;
 }