Moving to newly available `user_data` file purpose, which is a
"[f]lexible file type for any purpose". Files uploaded under the
`assistant` file purpose can be used with the new Responses API.

Azure OpenAI Service does not support the new `user_data` file purpose
and is excluded from this change:
https://learn.microsoft.com/en-us/azure/ai-foundry/openai/how-to/responses?tabs=python-secure#model-support