spring.ai.openai.chat.reasoning-effort not documented

[pcdavid]

Bug description

The spring.ai.openai.chat.reasoning-effort option is implemented, but contrary to the equivalent for DeepSeek or Mistral, it is not documented for OpenAI.

Steps to reproduce

1. Try to use Spring AI 2.0.0 with -Dspring.ai.openai.chat.model=gpt-5.6-terra.
2. As soon as a tool is invoked, you get:

400: Function tools with reasoning_effort are not supported for gpt-5.6-terra in /v1/chat/completions. To use function tools, use /v1/responses or set reasoning_effort to 'none'.

3. Look at the doc to see if this option is supported. It does not appear.
4. Try it anyway, with -Dspring.ai.openai.chat.reasoning-effort=none.
5. It actually works, just not documented.

Expected behavior

The OpenAI documentation should mention all supported options to avoid confusion.

[CryoThrust]

I opened PR #6943 with a documentation-only update for the existing OpenAI reasoning-effort property. It documents the property in the OpenAI chat options table and notes that values/model compatibility are determined by the OpenAI Chat Completions API, including the tool-calling case where none may be required. No runtime behavior is changed.