A good practice when authenticating with Azure OpenAI is using token providers.
Following then example of:
https://docs.litellm.ai/docs/providers/azure#azure-ad-token-refresh---defaultazurecredential

The reason for token provider vs. getting token is that the token expires with some time limit.

We get a type error that the token provider is not JSON serializable.

This was also experienced by @arthurgreef in #1561 (comment).
Although "fixed" by getting the token instead of providing the callable that handles refreshing of tokens.

I assume this is a byproduct of caching, but the behaviour is still present with cache=False parameter.