MongoDB CheckpointSaver: No date field available for TTL index support in current schema

[yishaistern]

I'm using the CheckpointSaver with MongoDB for persistence and would like to set up a TTL index to automatically expire old checkpoints. However, I noticed that the current MongoDB documents don't include a Date-type field that can be used for TTL purposes. It would be great to have a timestamp (e.g., createdAt) added to the saved checkpoints to support this use case.
at this point schema looks like this:
{ "_id": { "$oid": "" }, "checkpoint_id": "", "checkpoint_ns": "", "thread_id": "", "checkpoint": { "$binary": { "base64": "", "subType": "00" } }, "metadata": { "$binary": { "base64": "", "subType": "00" } }, "parent_checkpoint_id": "", "type": "json" }
None of these are Date type

[sdip0971]

Hey! Just opened a PR to implement this enhancement 👉 #1401

✅ Adds optional TTL support for MongoDB-based checkpoint saver using a _createdAtForTTL Date field
✅ Supports opt-in TTL cleanup with enableTTL flag
✅ Keeps backward compatibility — no breaking changes

Let me know if anything else is needed!