Spring-ai Add support for max_completion_tokens in OpenAI chat options request

Adds support for max_completion_tokens in OpenAI chat options request - An upper bound for the number of tokens that can be generated for a completion, including visible output tokens and reasoning tokens.

Fixes https://github.com/spring-projects/spring-ai/issues/1411

Comment From: tzolov

Thank you for the contribution @dafriz . Much appreciated

Comment From: tzolov

Rebased and merge at f56ce20cade7523396a2ce8728c856b0c0a159c0