Better validation for `account_name` in Planetary Computer credential provider

[kylebarron]

from obstore.auth.planetary_computer import PlanetaryComputerCredentialProvider
from obstore.store import AzureStore
import pystac_client

catalog = pystac_client.Client.open(
    "https://planetarycomputer.microsoft.com/api/stac/v1/"
)
asset = catalog.get_collection("io-lulc-9-class").assets["geoparquet-items"]

account_name = asset.extra_fields["table:storage_options"]
credential_provider = PlanetaryComputerCredentialProvider(
    url=asset.href,
    account_name=account_name,
)
store = AzureStore(credential_provider=credential_provider)

This gives a confusing error

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In[16], line 6
      1 account_name = asset.extra_fields["table:storage_options"]
      2 credential_provider = PlanetaryComputerCredentialProvider(
      3     url=asset.href,
      4     account_name=account_name,
      5 )
----> 6 store = AzureStore(credential_provider=credential_provider)

TypeError: argument 'credential_provider': 'dict' object cannot be converted to 'PyString'

It's because

credential_provider.config
# {'account_name': {'account_name': 'pcstacitems'}, 'container_name': 'items'}

we should have validation that account_name is a str