EPIC - Structured Output Improvements

[markpollack]

Most AI models now support an option to provide structured output.

1. Verify that the chat client options for all models that support structured output have a corresponding option.
2. BeanOutputConverter does not take advantage of this model feature, it relies on prompt engineering which isn't as robuts.
3. Review issues listed below for further actions/features.

[dev-jonghoonpark]

Issue #1854 can be resolved through PR #2754.

[mautini]

We have the same need here. It would be greatly appreciated to have this feature included in the 1.0 release. This PR (#2754) addresses it for OpenAPI, but other models—such as Gemini, Mistral, etc.—also natively support structured output. Are there any plans to support them as well, or is any help needed to make that happen?

[johnsonr]

This is becoming increasingly urgent, as gpt-4.1-mini is more and more often failing to respect JSON schema appended to the prompt. It's possible to work around it with few shot examples, but that's not ideal.

[apappascs]

I think this issue has been resolved for openai with this commit #1198 by @tzolov ?