## Threads
### Updates & Improvements
- The UI will depend on the `output_index` recorded by the server to
sort messages in threads instead of the created timestamp.
- Introduces `ThreadMessage` subclass that offers some improvements over
the original OpenAI SDK version:
    - `status` can be `None` for user messages.
    - `created_at` can be `float` for Next-Gen Assistants.
- `output_index`: The output index of the message, if applicable for
Next-Gen Assistants.
- `metadata` dictionary: This field can also include boolean values, in
addition to strings. This change resolves Pydantic serializer warnings
introduced when the boolean `is_current_user` value was added in the
`metadata` dictionary.