Add a End-to-end unit test for image embeddings and audio embeddings

### Feature request

image embeddings, and audio embeddings have currently insufficent coverage in the openai api server.

### Motivation

It would be great to have a test testing this end-to-end - and make infinity more stable!

### Your contribution

Happy to add you to the graph of contributors

First confirm that the request is still applicable, then inspect the openai API server's existing end-to-end test coverage for embeddings. Add coverage for both image embeddings and audio embeddings, and run the relevant test suite to verify the server handles both paths successfully.

Written by the indexing model from the issue text.