Support for Json Schema with Gemini

[aleksabl]

The current implementation allows passing a JSON schema to OpenAI using OpenAiChatOptions.setResponseFormat, where a ResponseFormat with a specified JSON schema can be provided. However, this functionality is not available in VertexAiGeminiChatOptions. In the latter, you can only specify the contentType without the ability to include a schema.

[kiruthiga1793]

Hi @aleksabl , I would like to collaborate to this issue. Can you please assign me this issue or can i work with you on this?

[aleksabl]

@kiruthiga1793 I'm just a regular user - I don't have any extra permissions. If you would have a go at it, you should try to fix it and create a pull request.