Support `response_json_schema` as a `method` for `with_structured_output`

[jovialis]

Starting in Gemini 2.5, Google supports full JSON schema as opposed to the previous subset of the OpenAPI spec that it previously supported.

https://ai.google.dev/gemini-api/docs/structured-output

This is specified in its response types by passing response_json_schema as opposed to its previous OpenAPI compatible schema, which was passed with response_schema.

The LangFuse Vertex AI package needs to be updated to support the new method, which will unlock support for using complex Pydantic models and JSON schemas with Gemini.

[hustxiayang]

Hi, does it work for gemini2.0 models? Many people are still using gemini2.0 models if that does not work for gemini2.0 models?

[jovialis]

@hustxiayang No -- only Gemini 2.5