Spring-ai Currently Vertex API uses one Tool per function definition, but tools can have multiple function inside

as described in issue #619 There are an API error with Gemini-Vertex API with multiple functions.

The "model" can admit multiple tools with multiple function inside. But if you specify two or more tools the Gemini API throw an 400 error.

Avoid this generating a single tool with all function inside.

Comment From: tzolov

Yeh, i appears that Gemini Pro model has broken functional calling support. You can non anymore specify function names like "getWeatherInfo" as the model rewrites those into get_weather_info". Furthermore the parallel function call is gone as well. Very disappointing. Not sure if there is any Google Gemini channel to report those issues.

Comment From: tzolov

I've updated the PR to make at least some of the IT test to work.
Also added a document warning about the functionality degradation: https://docs.spring.io/spring-ai/reference/1.0-SNAPSHOT/api/chat/vertexai-gemini-chat.html#_function_calling

Comment From: tzolov

Merged at 9f32a3ca9cd119116b112e050b942e5e94855914