feat: Add support for audio in chat completions in openai_dart

[davidmigloz]

In addition to generating text and images, some OpenAI models enable you to generate a spoken audio response to a prompt:

final res = await client.createChatCompletion(
  request: CreateChatCompletionRequest(
    model: ChatCompletionModel.model(
      ChatCompletionModels.gpt4oAudioPreview,
    ),
    modalities: [
      ChatCompletionModality.text,
      ChatCompletionModality.audio,
    ],
    audio: ChatCompletionAudioOptions(
      voice: ChatCompletionAudioVoice.alloy,
      format: ChatCompletionAudioFormat.wav,
    ),
    messages: [
      ChatCompletionMessage.user(
        content: ChatCompletionUserMessageContent.string(
          'Is a golden retriever a good family dog?',
        ),
      ),
    ],
  ), 
);
final choice = res.choices.first;
final audio = choice.message.audio;
print(audio?.id);
print(audio?.expiresAt);
print(audio?.transcript);
print(audio?.data);

And to use audio inputs to prompt the model:

final res = await client.createChatCompletion(
  request: CreateChatCompletionRequest(
    model: ChatCompletionModel.model(
      ChatCompletionModels.gpt4oAudioPreview,
    ),
    modalities: [
      ChatCompletionModality.text,
      ChatCompletionModality.audio,
    ],
    audio: ChatCompletionAudioOptions(
      voice: ChatCompletionAudioVoice.alloy,
      format: ChatCompletionAudioFormat.wav,
    ),
    messages: [
      ChatCompletionMessage.user(
        content: ChatCompletionUserMessageContent.parts([
          ChatCompletionMessageContentPart.text(
            text: 'Do what the recording says',
          ),
          ChatCompletionMessageContentPart.audio(
            inputAudio: ChatCompletionMessageInputAudio(
              data: 'UklGRoYZAQBXQVZFZm10I...//X//v8FAOj/GAD+/7z/',
              format: ChatCompletionMessageInputAudioFormat.wav,
            ),
          ),
        ]),
      ),
    ],
  );
);
final choice = res.choices.first;
final audio = choice.message.audio;
print(audio?.id);
print(audio?.expiresAt);
print(audio?.transcript);
print(audio?.data);

Docs:

• https://platform.openai.com/docs/guides/audio