Support fileId for ImagePart

[Godrules500]

Feature Description

I am adding the ability to attach images (and hopefully non images) to my app, in which some of this data will be confidential so public URLs won't work. The issue I am running into now is, I am storing the chat history in a dynamo db table which has a pretty low limit that images and files quickly exceed so I am storing the images in an s3 bucket. This is proving to be more challenging, because I have to pull out the base64 string, and replace it with the fileId before updating the db. I am on a stateless server, so I am storing the fileId in the aiState.

I am wanting to store the fileId (or any other field(s)) that make sense, so that I can store it in dynamoDb.

Or if there is another, better way, I am all ears!

Use Case

Storing files in a different location than the chat history.

Additional context

No response