Replace message handling with a chat session model, aligning the logic with new API requirements. Adjust functions to properly build chat history and send messages via chat sessions, improving compatibility and extensibility.
Implemented a nil check for Toolbox to prevent potential nil pointer dereferences. Cleaned up and reorganized code for better readability and maintainability while keeping placeholder functionality intact.
Modify `FunctionCall` struct to handle arguments as strings. Add debugging logs to facilitate error tracing and improve JSON unmarshalling in various functions.
