Improve tool call message processing (#3036)
* make content field optional in chat request
* add tool_calls field to Message struct
* feat: add test and serialize tool messages
* fix: bump utopia, openapi doc version and improve test
* fix: rerun update docs
* fix: suppoer tool call id in template and remove unnecessary changes
* fix: ruff lint remove unused import
* fix: adjust message types in tests
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Co-authored-by: sailesh duddupudi <saileshradar@gmail.com>
