chore: migrate to new backend in local development

additionally allow defining custom sidebar item for dev app page.

Signed-off-by: Heikki Hellgren <heikki.hellgren@op.fi>

plugins/signals-backend/dev/index.ts

@@ -0,0 +1,59 @@
+/*
+ * Copyright 2024 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 { createBackend } from '@backstage/backend-defaults';
+import {
+  coreServices,
+  createBackendPlugin,
+} from '@backstage/backend-plugin-api';
+import { signalService } from '@backstage/plugin-signals-node';
+
+const signalDebug = createBackendPlugin({
+  pluginId: 'signals-debug',
+  register(env) {
+    env.registerInit({
+      deps: {
+        signals: signalService,
+        lifecycle: coreServices.lifecycle,
+      },
+      async init({ signals, lifecycle }) {
+        let interval: NodeJS.Timeout | undefined;
+        lifecycle.addStartupHook(async () => {
+          interval = setInterval(async () => {
+            await signals.publish<{ date: string }>({
+              channel: 'debug',
+              message: { date: new Date().toISOString() },
+              recipients: { type: 'broadcast' },
+            });
+          }, 1000);
+        });
+
+        lifecycle.addShutdownHook(async () => {
+          if (interval) {
+            clearInterval(interval);
+          }
+        });
+      },
+    });
+  },
+});
+
+const backend = createBackend();
+backend.add(import('@backstage/plugin-events-backend/alpha'));
+backend.add(import('../src'));
+backend.add(signalDebug);
+
+backend.start();