Fix front-end unit tests (#2529)

This doesn't really add any tests, and we'll require many more additions
if we actually want to have full unit testing, but this at least makes
the tests pass when running `npm test`.

console-webapp/src/testdata/registrar/registrar.service.mock.ts

@@ -0,0 +1,21 @@
+// Copyright 2024 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import { RegistrarService } from 'src/app/registrar/registrar.service';
+
+export const MOCK_REGISTRAR_SERVICE = {
+  registrar: function () {
+    return { ipAddressAllowList: ['123.123.123.123'] };
+  },
+} as RegistrarService;