Storage clients should handle AzureNamedKeyCredential as credential

[bluenote10]

Is your feature request related to a problem? Please describe.

The storage clients (blob, queue, ...) doesn't seem to support the type AzureNamedKeyCredential. This is inconsistent with many other parts of the API. For instance the table client allows it:

azure-sdk-for-python/sdk/tables/azure-data-tables/azure/data/tables/_base_client.py

Lines 76 to 82 in c8a0268

	class AccountHostsMixin(object): # pylint: disable=too-many-instance-attributes
	def __init__(
	self,
	account_url, # type: Any
	credential=None, # type: Optional[Union[AzureNamedKeyCredential, AzureSasCredential, "TokenCredential"]]
	**kwargs # type: Any
	):

It is also frustrating that the credential is typed as Any.

azure-sdk-for-python/sdk/storage/azure-storage-blob/azure/storage/blob/_shared/base_client.py

Line 71 in c8a0268

credential=None, # type: Optional[Any]

This causes a lot of guessing what kind of credential the clients support 😕

Describe the solution you'd like

The signature should get proper type annotations, and this function should simply handle AzureNamedKeyCredential.

azure-sdk-for-python/sdk/storage/azure-storage-blob/azure/storage/blob/_shared/base_client.py

Lines 348 to 359 in c8a0268

	def _format_shared_key_credential(account_name, credential):
	if isinstance(credential, six.string_types):
	if not account_name:
	raise ValueError("Unable to determine account name for shared key credential.")
	credential = {"account_name": account_name, "account_key": credential}
	if isinstance(credential, dict):
	if "account_name" not in credential:
	raise ValueError("Shared key credential missing 'account_name")
	if "account_key" not in credential:
	raise ValueError("Shared key credential missing 'account_key")
	return SharedKeyCredentialPolicy(**credential)
	return credential

Perhaps the private type SharedKeyCredentialPolicy should be even completely be replaced by AzureNamedKeyCredential.

Describe alternatives you've considered

Type guessing and constantly converting from and to AzureNamedKeyCredential and the plain {"account_name": str, "account_key": str} that the blob storage wants.

[kashifkhan]

@bluenote10 Thanks for your feedback, we'll investigate asap.

[annatisch]

Thanks for this report @bluenote10!
You're 100% correct - this should be added. AzureNamedKeyCredential was added to Azure Core some time after the first stable Storage SDK releases - and it looks like we forgot to go back and add support for it. Thanks for calling this out. :)