RealtimeServerEventResponseContentPartAdded

Returned when a new content part is added to an assistant message item during
response generation.

{
    "event_id": "string",
    "type": "response.content_part.added",
    "response_id": "string",
    "item_id": "string",
    "output_index": 0,
    "content_index": 0,
    "part": {
        "type": "audio",
        "text": "string",
        "audio": "string",
        "transcript": "string"
    }
}