Baseten.co: Add reasoning field for reasoning parser + grammar mode

[michaelfeil]

Hey,

we @basetenlabs / @NVIDIA are using your crate to run validations and output return.

Two things are missing in the Rust crate over e.g. the Python types.

• https://github.com/openai/openai-python/blob/4ada66f8f86473f342aa032ed021b62180422dc1/src/openai/types/shared/response_format_text_grammar.py#L10 grammar field.
• adds the reasoning field for the reasoning content https://openrouter.ai/docs/use-cases/reasoning-tokens

[64bit]

Thanks for the PR, however please see contribution guidelines for the scope of crate.

You can achieve this with combination of byot feature and Serde https://serde.rs/attr-flatten.html#struct-flattening to re-use/expand existing types.

[michaelfeil]

@64bit Do you have guidelines ? looked on crates.io and a contribution.md