Support Function calling

[mscheong01]

OpenAI has added "function calling" feature to the Chat api
https://openai.com/blog/function-calling-and-other-api-updates

We could leverage this feature to allow interfAIce proxies to call upon other methods
ex)

interface FunctionAware<T> {
    fun withFunction( ... ): T
    fun withFunctions( ... ): T
}
interface WeatherService : FunctionAware<WeatherService> {
    fun getWeather(): Weather
}

val proxy = OpenAiProxyFactory.of("sk-****").create<WeatherService>()
proxy
    .withFunction(weatherClient::greet)
    .getWeather()

[mscheong01]

https://github.com/openai/openai-cookbook/blob/main/examples/How_to_call_functions_with_chat_models.ipynb