Returned when a conversation item is created. There are several scenarios that
produce this event:

• The server is generating a Response, which if successful will produce
  either one or two Items, which will be of type message
  (role assistant) or type function_call.
• The input audio buffer has been committed, either by the client or the
  server (in server_vad mode). The server will take the content of the
  input audio buffer and add it to a new user message Item.
• The client has sent a conversation.item.create event to add a new Item
  to the Conversation.

Returned when an item in the conversation is deleted by the client with a
conversation.item.delete event. This event is used to synchronize the
server’s understanding of the conversation history with the client’s view.

This event is the output of audio transcription for user audio written to the
user audio buffer. Transcription begins when the input audio buffer is
committed by the client or server (in server_vad mode). Transcription runs
asynchronously with Response creation, so this event may come before or after
the Response events.

Realtime API models accept audio natively, and thus input transcription is a
separate process run on a separate ASR (Automatic Speech Recognition) model,
currently always whisper-1. Thus the transcript may diverge somewhat from
the model’s interpretation, and should be treated as a rough guide.

Returned when input audio transcription is configured, and a transcription
request for a user message failed. These events are separate from other
error events so that the client can identify the related Item.

Returned when an earlier assistant audio message item is truncated by the
client with a conversation.item.truncate event. This event is used to
synchronize the server’s understanding of the audio with the client’s playback.

This action will truncate the audio and remove the server-side text transcript
to ensure there is no text in the context that hasn’t been heard by the user.