Add support for OpenAI's Predicted Outputs

[aretrace]

OpenAI released a new api feature called Predicted Outputs. It's designed to reduce latency when most of the output is already known in advance. This is especially useful for tasks that involve minor changes to existing content (maybe like structured data transformations 😁).

[karljuhlthefool]

Upvote. Although function calling isn't supported with predicted outputs, the json mode should be implemented.