Add support for predicted outputs in OpenAIModelSettings

[webholics]

Description

I would be nice to add support for prediction in OpenAIModelSettings.

Also when it comes to predictions it would also be helpful to be able to define model_settings of an agent depending on the provided RunContext.
Something like:

@my_agent.model_settings
def define_model_settings(
    ctx: RunContext[MyAgentDeps],
) -> ModelSettings:
    return OpenAIModelSettings(prediction=ctx.example_state)

References

https://platform.openai.com/docs/guides/predicted-outputs

[DouweM]

@webholics Makes sense! As it's currently only supported by OpenAI, we'd need to add it to OpenAIModelSettings only with an openai_ prefix. Would you be up for submitting a PR?

[webholics]

I will prepare one