Add DefaultAzureCredential auth mechanism support #662
Description
The current ObjectStore API doesn't support authenticating to Azure using DefaultAzureCredential. This is a limitation in AKS environments where managed-identities are not configured.
Even if the environment is configured to use the app Service Principal with variables AZURE_CLIENT_ID, AZURE_TENANT_ID, and AZURE_CLIENT_SECRET the barman-cloud client attempts to authenticate using the managed-identity and fails if not available.