Introduce V1 namespaces in StripeClient (#1549)

* Introduced V1 namespaces

* Updated migration guide link

Author: prathmesh-stripe

stripe/__init__.py

@@ -567,6 +567,7 @@ def __getattr__(name):
 )
 from stripe._transfer_service import TransferService as TransferService
 from stripe._treasury_service import TreasuryService as TreasuryService
+from stripe._v1_services import V1Services as V1Services
 from stripe._v2_services import V2Services as V2Services
 from stripe._webhook_endpoint import WebhookEndpoint as WebhookEndpoint
 from stripe._webhook_endpoint_service import (