feat(demo): add isolated demo environments

apps/notifications/services/store.py

@@ -205,6 +205,18 @@ class RedisNotificationStore:
             return True
         return False
 
+    @classmethod
+    def clear_user(cls, user_id: str) -> int:
+        ids_key = cls._ids_key(user_id)
+        data_key = cls._data_key(user_id)
+        count = redis_client.zcard(ids_key)
+        pipe = redis_client.pipeline()
+        pipe.delete(ids_key)
+        pipe.delete(data_key)
+        pipe.srem(cls.USERS_KEY, user_id)
+        pipe.execute()
+        return int(count or 0)
+
     @classmethod
     def mark_seen(cls, user_id: str, notif_id: str) -> dict | None:
         data = cls.get(user_id, notif_id)