Add new otid field to Message API

The Message object returned by our Messages endpoints now includes an offline threading id field, a unique identifier set at creation time, which can be used by the client to deduplicate messages.

Before:

1from letta_client import Letta, MessageCreate
2import uuid
3client = Letta(
4 token="YOUR_API_KEY",
5)
6messages = client.agents.messages.create(
7 agent_id="AGENT_ID",
8 messages=[
9 MessageCreate(
10 role="user",
11 content="Hello, how are you?"
12 otid=uuid.uuid4(),
13 )
14 ]
15)