Update key storage toggle when key storage status changes (#30934)

* update key storage toggle when key storage status changes

Listen for the CryptoEvent.KeyBackupStatus event and update the state
when it changes.

* fixup! update key storage toggle when key storage status changes

* add comment about handling event

playwright/e2e/crypto/crypto.spec.ts

@@ -146,6 +146,29 @@ test.describe("Cryptography", function () {
         }).toPass();
     });
 
+    // When the user resets their identity, key storage also gets enabled.
+    // Check that the toggle updates to show the correct state.
+    test("Key backup status updates after resetting identity", async ({ page, app, user: aliceCredentials }) => {
+        await app.client.bootstrapCrossSigning(aliceCredentials);
+
+        const encryptionTab = await app.settings.openUserSettings("Encryption");
+        const keyStorageToggle = encryptionTab.getByRole("switch", { name: "Allow key storage" });
+        // Check that key storage starts off as disabled
+        expect(await keyStorageToggle.isChecked()).toBe(false);
+        // Find "the Reset cryptographic identity" button
+        await encryptionTab.getByRole("button", { name: "Reset cryptographic identity" }).click();
+
+        // Confirm
+        await encryptionTab.getByRole("button", { name: "Continue" }).click();
+
+        // Enter the password
+        await page.getByPlaceholder("Password").fill(aliceCredentials.password);
+        await page.getByRole("button", { name: "Continue" }).click();
+
+        // Key storage should now be enabled
+        expect(await keyStorageToggle.isChecked()).toBe(true);
+    });
+
     test(
         "creating a DM should work, being e2e-encrypted / user verification",
         { tag: "@screenshot" },