Add opt-in per-device browser notifications for account interactions

Hop-State: A_06FPDJBMCPFBTW71R7MJ6A0
Hop-Proposal: R_06FPDJB4CE0WHS7ZKV9KFS0
Hop-Task: T_06FPDHJ54908E4K96KJA0K0
Hop-Attempt: AT_06FPDHJ54AYSSF1D1H293N0

src/lib/notifications/browser.test.ts

@@ -0,0 +1,39 @@
+import { describe, expect, it } from 'vitest';
+
+import {
+    browserNotificationsEnabledKey,
+    getBrowserNotificationContent,
+} from './browser';
+
+describe('browser notification presentation', () => {
+    it('scopes the opt-in to the signed-in account', () => {
+        expect(browserNotificationsEnabledKey('user-1'))
+            .toBe('synapsis:browser-notifications:user-1');
+    });
+
+    it('links post interactions to the relevant post', () => {
+        expect(getBrowserNotificationContent({
+            id: 'notification-1',
+            type: 'like',
+            actor: { handle: 'alice', displayName: 'Alice' },
+            post: { id: 'post-1', content: 'A post worth liking' },
+        })).toEqual({
+            title: 'Alice liked your post',
+            body: 'A post worth liking',
+            url: '/posts/post-1',
+            tag: 'synapsis-notification-notification-1',
+        });
+    });
+
+    it('uses the notifications page when there is no post', () => {
+        expect(getBrowserNotificationContent({
+            id: 'notification-2',
+            type: 'follow',
+            actor: { handle: 'bob', displayName: null },
+            post: null,
+        })).toMatchObject({
+            title: 'bob followed you',
+            url: '/notifications',
+        });
+    });
+});