Overrides the built-in fallback values used by default_azure_host(),
default_azure_client_id(), and default_azure_tenant_id() when the
corresponding environment variable is not set. Pass NULL to a parameter
to clear a previously set override.
The priority order for each default is:
Package-level override set by set_azr_defaults() (highest)
Environment variable (AZURE_AUTHORITY_HOST, AZURE_CLIENT_ID,
AZURE_TENANT_ID)
Built-in fallback (lowest)