Support for DefaultAzureCredential with pl.read/scan_delta()

[drumtorben]

With the latest Polars version 1.20.0, it should be possible to read tables from Azure directly using DefaultAzureCredential under the hood.

However, I encountered an issue when trying to use pl.read/scan_delta(). These functions seem to still require me to explicitly provide storage_options={"bearer_token": "<token>"} for authentication.

Here are the details of my setup:

• Storage format: The path starts with "abfs://...".
• Question: Could the issue be related to this specific storage format? Or is DefaultAzureCredential support not yet implemented for this type of storage?

Steps to Reproduce:

1. Attempt to use pl.read/scan_delta() on an Azure storage account using a path that starts with "abfs://...".
2. Ensure DefaultAzureCredential is configured and available in the environment.
3. Observe whether it works without providing storage_options manually.

Expected Behavior:
DefaultAzureCredential should handle authentication seamlessly, as described for other storage types in the documentation.

Observed Behavior:
Authentication fails unless storage_options are explicitly provided with a bearer token.

Environment Details:

• Polars Version: 1.20.0
• Azure Storage Type: abfs://

Additional Context:
If this feature isn’t supported yet for "abfs://...", it would be great to have clarity on whether it’s planned or if there are workarounds.