New mail in the other signed-in accounts: counts, a dot, and a notification

With more than one account signed in (#49), mail arriving in one that
isn't in front went unseen until someone switched to it (multi-account
spec, MA-8).

- GET /api/auth/accounts/unread answers the Inbox unread count of each
  account not in front, asked through that account's own session (its
  OAuth token renewed first if due), kept a minute per account.
- The web app asks every two minutes while another account is signed
  in. The account menu shows each one's count beside its name, and the
  avatar carries a dot when any of them has unread mail.
- When a count rises while the app is open and desktop notifications
  are on, a notification names the account ("New mail for
  [email protected]"); clicking it switches to that account. An
  account seen for the first time doesn't notify: its mail was already
  there.

Not in this change: notifications with the app closed, which need each
added account's own Web Push subscription.

New strings (3, English only in the other ten catalogs): "New mail for
{name}", "Unread in the Inbox: {count}", "Account: new mail in another
account". Tests: the server answers the other account's count and
nothing when alone; the client keeps the counts, notifies only on a
rise and only with notifications on. Checked in Chrome against the
mock. typecheck, tests (web 1541, server 277) and build pass.

web/src/lib/__tests__/other-accounts.test.ts

@@ -0,0 +1,68 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+
+/** inbuxa MA-8: new mail in the accounts not in front. */
+
+const shown: { title: string; opts: Record<string, unknown> }[] = [];
+vi.mock("@/lib/notify/notify", () => ({
+  showNotification: (title: string, opts: Record<string, unknown>) => shown.push({ title, opts }),
+}));
+
+const { risen, pollOtherUnread, useOtherUnread } = await import("@/lib/otherAccounts");
+const { useSession } = await import("@/store/session");
+const { useSettings } = await import("@/store/settings");
+
+let counts: Record<string, number>;
+
+beforeEach(() => {
+  shown.length = 0;
+  counts = { b: 3 };
+  vi.stubGlobal(
+    "fetch",
+    vi.fn(async () => {
+      const body = { accounts: Object.entries(counts).map(([id, unread]) => ({ id, unread })) };
+      return { ok: true, status: 200, json: async () => body, text: async () => JSON.stringify(body) } as Response;
+    }),
+  );
+  useOtherUnread.getState().set({});
+  useSession.setState({
+    signedIn: [
+      { id: "a", username: "[email protected]", front: true },
+      { id: "b", username: "[email protected]", front: false },
+    ],
+  });
+  useSettings.setState((s) => ({ settings: { ...s.settings, desktopNotifications: true } }));
+});
+
+afterEach(() => {
+  vi.unstubAllGlobals();
+});
+
+describe("other accounts' unread mail", () => {
+  it("counts only a rise, and never an account seen for the first time", () => {
+    expect(risen({}, { b: 4 })).toEqual([]);
+    expect(risen({ b: 4 }, { b: 4 })).toEqual([]);
+    expect(risen({ b: 4 }, { b: 2 })).toEqual([]);
+    expect(risen({ b: 4, c: 1 }, { b: 5, c: 1 })).toEqual(["b"]);
+  });
+
+  it("keeps the counts, and names the account when new mail arrives", async () => {
+    await pollOtherUnread();
+    expect(useOtherUnread.getState().unread).toEqual({ b: 3 });
+    expect(shown).toEqual([]);
+
+    counts = { b: 5 };
+    await pollOtherUnread();
+    expect(shown).toHaveLength(1);
+    expect(shown[0]!.title).toContain("[email protected]");
+    expect(shown[0]!.opts.tag).toBe("other-account-b");
+  });
+
+  it("stays quiet when desktop notifications are off", async () => {
+    useSettings.setState((s) => ({ settings: { ...s.settings, desktopNotifications: false } }));
+    await pollOtherUnread();
+    counts = { b: 9 };
+    await pollOtherUnread();
+    expect(shown).toEqual([]);
+    expect(useOtherUnread.getState().unread).toEqual({ b: 9 });
+  });
+});