Improve Example Code to Correctly Error Out when OP_SERVICE_ACCOUNT_TOKEN is not set. (#95)

* Fix example to correctly show error when OP_SERVICE_ACCOUNT_TOKEN is not set

* Revert example.py change and add it to client.py

* Remove optional from auth and add it directly to the new_defualt_config

* Remove unnecessary import

* Remove unnecessary comment addition

Author: MOmarMiraj

src/onepassword/client.py

@@ -14,8 +14,9 @@ class Client:
 
     @classmethod
     async def authenticate(cls, auth, integration_name, integration_version):
+        # Convert None from os.getEnv to empty string
         config = new_default_config(
-            auth=auth,
+            auth=auth or "",
             integration_name=integration_name,
             integration_version=integration_version,
         )