implement some of the trivial backend plugins

Signed-off-by: Fredrik Adelöw <freben@gmail.com>

plugins/user-settings-backend/src/index.ts

@@ -16,3 +16,4 @@
 
 export * from './service';
 export * from './database';
+export { userSettingsPlugin } from './plugin';

plugins/user-settings-backend/src/plugin.ts

@@ -0,0 +1,42 @@
+/*
+ * Copyright 2023 The Backstage Authors
+ *
+ * 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 {
+  createBackendPlugin,
+  coreServices,
+} from '@backstage/backend-plugin-api';
+import { createRouter } from './service/router';
+
+/**
+ * The user settings backend plugin.
+ *
+ * @alpha
+ */
+export const userSettingsPlugin = createBackendPlugin({
+  id: 'userSettings',
+  register(env) {
+    env.registerInit({
+      deps: {
+        database: coreServices.database,
+        identity: coreServices.identity,
+        httpRouter: coreServices.httpRouter,
+      },
+      async init({ database, identity, httpRouter }) {
+        httpRouter.use(await createRouter({ database, identity }));
+      },
+    });
+  },
+});