[Question] Azure OpenAI - Latest API version missing "image" message content for Assistant API

### API Spec link

https://github.com/Azure/azure-rest-api-specs/tree/main/specification/cognitiveservices/data-plane/AzureOpenAI

### API Spec version

2024-07-01-preview

### Question/Query

## Message Content
When trying to add non-text messages we get an error message indicating only "text" is allowed. OpenAI has supported this for a couple months so it's surprising to see this missing still. Do we have an ETA on when this will be added?
```py
await client.beta.threads.messages.create(
thread_id=thread.id,
role="user",
content=[{'text': 'what does this say?', 'type': 'text'}, {'image_url': {'url': 'data:image/png;base64,iVBORw0KG...', 'detail': 'auto'}, 'type': 'image_url'}]
)
```
```bash
openai.BadRequestError: Error code: 400 - {'error': {'message': "Invalid message content: only messages with 'type=text' are supported currently.", 'type': 'invalid_request_error', 'param': 'content', 'code': 'invalid_type'}}
```

### Environment

_No response_

Start with the specification/cognitiveservices/data-plane/AzureOpenAI path linked in the issue and inspect the 2024-07-01-preview definition for Assistant API message content. Compare its supported content types with the reported Python request and error; done would require a documented, accepted image message shape and confirmation that the Azure endpoint supports it.

Written by the indexing model from the issue text.