docs: add installation documentation for notifications

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

plugins/notifications-backend/README.md

@@ -2,13 +2,38 @@
 
 Welcome to the notifications backend plugin!
 
-_This plugin was created through the Backstage CLI_
-
 ## Getting started
 
-Your plugin has been added to the example app in this repository, meaning you'll be able to access it by running `yarn
-start` in the root directory, and then navigating to [/notifications](http://localhost:3000/notifications).
+First you have to install the `@backstage/plugin-notifications-node` package.
 
-You can also serve the plugin in isolation by running `yarn start` in the plugin directory.
-This method of serving the plugin provides quicker iteration speed and a faster startup and hot reloads.
-It is only meant for local development, and the setup for it can be found inside the [/dev](/dev) directory.
+Then create a new file to `packages/backend/src/plugins/notifications.ts`:
+
+```ts
+import { createRouter } from '@backstage/plugin-notifications-backend';
+import { Router } from 'express';
+import { PluginEnvironment } from '../types';
+
+export default async function createPlugin(
+  env: PluginEnvironment,
+): Promise<Router> {
+  return await createRouter({
+    logger: env.logger,
+    identity: env.identity,
+    notificationService: env.notificationService,
+  });
+}
+```
+
+and add it to `packages/backend/src/index.ts`:
+
+```ts
+async function main() {
+  //...
+  const notificationsEnv = useHotMemoize(module, () =>
+    createEnv('notifications'),
+  );
+
+  // ...
+  apiRouter.use('/notifications', await notifications(notificationsEnv));
+}
+```

plugins/notifications-node/README.md

@@ -2,4 +2,57 @@
 
 Welcome to the Node.js library package for the notifications plugin!
 
-_This plugin was created through the Backstage CLI_
+## Getting Started
+
+To be able to send notifications from other backend plugins, the `NotificationService` must be initialized for the
+environment. This can be done by adding the following changes to `packages/backend/src/index.ts` and
+`packages/backend/src/types.ts`:
+
+`index.ts`:
+
+```ts
+import { NotificationService } from '@backstage/plugin-notifications-node';
+
+function makeCreateEnv(config: Config) {
+  // ...
+  const notificationService = NotificationService.create({
+    database: databaseManager.forPlugin('notifications'),
+    discovery,
+  });
+  // ...
+  return (plugin: string): PluginEnvironment => {
+    // ...
+    return {
+      // ...
+      notificationService,
+    };
+  };
+}
+```
+
+`types.ts`:
+
+```ts
+import { NotificationService } from '@backstage/plugin-notifications-node';
+export type PluginEnvironment = {
+  // ...
+  notificationService: NotificationService;
+};
+```
+
+You also need to set up the `@backstage/plugin-notifications-backend` and `@backstage/plugin-notifications`
+to be able to show notifications in the UI.
+
+## Sending notifications
+
+To send notifications from backend plugin, use the `NotificationService::send` functionality. This function will
+save the notification and optionally signal the frontend to show the latest status for users.
+
+When sending notifications, you can specify the entity reference of the notification. If the entity reference is
+a user, the notification will be sent to only that user. If it's a group, the notification will be sent to all
+members of the group. If it's some other entity, the notification will be sent to the owner of that entity.
+
+## Extending Notification Service
+
+The `NotificationService` can be extended with `NotificationProcessor`. These processors allow to decorate notifications
+before they are sent or/and send the notifications to external services.

plugins/notifications/README.md

@@ -6,8 +6,36 @@ _This plugin was created through the Backstage CLI_
 
 ## Getting started
 
-Your plugin has been added to the example app in this repository, meaning you'll be able to access it by running `yarn start` in the root directory, and then navigating to [/notifications](http://localhost:3000/notifications).
+First, install the `@backstage/plugin-notifications-backend` and `@backstage/plugin-notifications-node` packages.
+See the documentation for installation instructions.
 
-You can also serve the plugin in isolation by running `yarn start` in the plugin directory.
-This method of serving the plugin provides quicker iteration speed and a faster startup and hot reloads.
-It is only meant for local development, and the setup for it can be found inside the [/dev](./dev) directory.
+To add the notifications main menu, add the following to your `packages/app/src/components/Root/Root.tsx`:
+
+```tsx
+import { NotificationsSidebarItem } from '@backstage/plugin-notifications';
+
+<SidebarPage>
+  <Sidebar>
+    <SidebarGroup>
+      // ...
+      <NotificationsSidebarItem />
+    </SidebarGroup>
+  </Sidebar>
+</SidebarPage>;
+```
+
+Also add the route to notifications to `packages/app/src/App.tsx`:
+
+```tsx
+import { NotificationsPage } from '@backstage/plugin-notifications';
+
+<FlatRoutes>
+  // ...
+  <Route path="/notifications" element={<NotificationsPage />} />
+</FlatRoutes>;
+```
+
+## Real-time notifications
+
+To be able to get real-time notifications to the UI without need for the user to refresh the page, you also need to
+add `@backstage/plugin-signals` package to your installation.