phsl / new-api

- Changed the type of ToolCalls in the Message struct from `any` to `json.RawMessage` for better type safety and clarity.
- Introduced ParseToolCalls and SetToolCalls methods to handle ToolCalls more effectively, improving code readability and maintainability.
- Updated the ParseContent method to work with the new MediaContent type instead of MediaMessage, enhancing the structure of content parsing.
- Refactored Gemini relay functions to utilize the new ToolCalls handling methods, streamlining the integration with OpenAI and Gemini systems.