nixos/network-interfaces: add assertion if used in after or wants

nixos/modules/system/boot/systemd.nix

@@ -451,6 +451,21 @@ in
         cfg.services
     );
 
+    assertions = concatLists (
+      mapAttrsToList
+        (name: service:
+          map (message: {
+            assertion = false;
+            inherit message;
+          }) (concatLists [
+            (optional ((builtins.elem "network-interfaces.target" service.after) || (builtins.elem "network-interfaces.target" service.wants))
+              "Service '${name}.service' is using the deprecated target network-interfaces.target, which no longer exists. Using network.target is recommended instead."
+            )
+          ])
+        )
+        cfg.services
+    );
+
     system.build.units = cfg.units;
 
     system.nssModules = [ cfg.package.out ];