Fix chat reponse deserialization with no toolCalls

[guersam]

Currently, missing toolCalls causes a deserialization error when there are no tools:

OpenAISyncClient(secret).createChatCompletion(ChatBody(
  model = ChatCompletionModel.GPT4Turbo,
  messages = Seq(
    Message.UserMessage(
      content = Content.TextContent("Hello!")
    )
  )
))

Fail(sttp.openai.OpenAIExceptions$OpenAIException$DeserializationOpenAIException: missing keys in dictionary: toolCalls at index 352

This commit sets default value for toolCalls to avoid the error.

[DybekK]

Thank you for your contribution 😃

[guersam]

My bad. At least in Scala 3, even with the default function argument, it still fails to deserialize when there are no toolCalls field in the JSON response 😢

Sorry again, I updated my build.sbt a few days go but forgot to refresh my SBT shell... Now it works as expected.