Bug 1893277 - build initial UI for turning on scheduled backups. r=backup-reviewers,firefox-desktop-core-reviewers ,fluent-reviewers,mconley

backup-settings changes:
- adds a new button in the Backup section of about:preferences / about:settings
- shows the turn on dialog after pressing the button

Turn on dialog behaviour (implemented):
- pressing the cancel will close the dialog
- pressing the confirm button will set the pref browser.backup.scheduled.enabled=true and close the dialog
- pressing the passwords checkbox will show more options

Turn on dialog behaviour (not implemented):
- requiring a password for the backup (see Bug 1895981)
- modifying the save location and showing a file picker (see Bug 1895943)

Other changes:
- tests for backup-settings and the turn on dialog
- Storybook template for the turn on dialog

Lo-fi Figma designs: https://www.figma.com/design/vNbX4c0ws0L1qr0mxpKvsW/Fx-Backup?node-id=147-4558&t=PYLY0QMN1n8GR9vW-0

Differential Revision: https://phabricator.services.mozilla.com/D209769

browser/components/backup/BackupService.sys.mjs

@@ -4,7 +4,9 @@
 
 import * as DefaultBackupResources from "resource:///modules/backup/BackupResources.sys.mjs";
 import { AppConstants } from "resource://gre/modules/AppConstants.sys.mjs";
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
 
+const SCHEDULED_BACKUPS_ENABLED_PREF_NAME = "browser.backup.scheduled.enabled";
 const lazy = {};
 
 ChromeUtils.defineLazyGetter(lazy, "logConsole", function () {
@@ -33,6 +35,19 @@ ChromeUtils.defineLazyGetter(lazy, "ZipWriter", () =>
   Components.Constructor("@mozilla.org/zipwriter;1", "nsIZipWriter", "open")
 );
 
+XPCOMUtils.defineLazyPreferenceGetter(
+  lazy,
+  "scheduledBackupsPref",
+  SCHEDULED_BACKUPS_ENABLED_PREF_NAME,
+  false,
+  function onUpdateScheduledBackups(_pref, _prevVal, newVal) {
+    let bs = BackupService.get();
+    if (bs) {
+      bs.onUpdateScheduledBackups(newVal);
+    }
+  }
+);
+
 /**
  * The BackupService class orchestrates the scheduling and creation of profile
  * backups. It also does most of the heavy lifting for the restoration of a
@@ -94,7 +109,11 @@ export class BackupService extends EventTarget {
    *
    * @type {object}
    */
-  #_state = { backupInProgress: false };
+  #_state = {
+    backupFilePath: "Documents", // TODO: make save location configurable (bug 1895943)
+    backupInProgress: false,
+    scheduledBackupsEnabled: lazy.scheduledBackupsPref,
+  };
 
   /**
    * A Promise that will resolve once the postRecovery steps are done. It will
@@ -844,6 +863,35 @@ export class BackupService extends EventTarget {
     }
   }
 
+  /**
+   * Sets browser.backup.scheduled.enabled to true or false.
+   *
+   * @param { boolean } shouldEnableScheduledBackups true if scheduled backups should be enabled. Else, false.
+   */
+  setScheduledBackups(shouldEnableScheduledBackups) {
+    Services.prefs.setBoolPref(
+      SCHEDULED_BACKUPS_ENABLED_PREF_NAME,
+      shouldEnableScheduledBackups
+    );
+  }
+
+  /**
+   * Updates scheduledBackupsEnabled in the backup service state. Should be called every time
+   * the value for browser.backup.scheduled.enabled changes.
+   *
+   * @param {boolean} isScheduledBackupsEnabled True if scheduled backups are enabled. Else false.
+   */
+  onUpdateScheduledBackups(isScheduledBackupsEnabled) {
+    if (this.#_state.scheduledBackupsEnabled != isScheduledBackupsEnabled) {
+      lazy.logConsole.debug(
+        "Updating scheduled backups",
+        isScheduledBackupsEnabled
+      );
+      this.#_state.scheduledBackupsEnabled = isScheduledBackupsEnabled;
+      this.stateUpdate();
+    }
+  }
+
   /**
    * Take measurements of the current profile state for Telemetry.
    *