Notifications: Cleaned up mails, added debounce for updates

- Updated mail notification design to be a bit prettier, and extracted
  text to new lang file for translation.
- Added debounce logic for page update notifications.
- Fixed watch options not being filtered to current user.

app/Activity/Notifications/Messages/BaseActivityNotification.php

@@ -3,6 +3,7 @@
 namespace BookStack\Activity\Notifications\Messages;
 
 use BookStack\Activity\Models\Loggable;
+use BookStack\Activity\Notifications\MessageParts\LinkedMailMessageLine;
 use BookStack\Users\Models\User;
 use Illuminate\Bus\Queueable;
 use Illuminate\Notifications\Messages\MailMessage;
@@ -47,4 +48,16 @@ abstract class BaseActivityNotification extends Notification
             'activity_creator' => $this->user,
         ];
     }
+
+    /**
+     * Build the common reason footer line used in mail messages.
+     */
+    protected function buildReasonFooterLine(): LinkedMailMessageLine
+    {
+        return new LinkedMailMessageLine(
+            url('/preferences/notifications'),
+            trans('notifications.footer_reason'),
+            trans('notifications.footer_reason_link'),
+        );
+    }
 }