Add backwards compatibility layer to SettingsApi change (#464)

Author: davidmrdavid

azure/durable_functions/decorators/durable_app.py

@@ -7,9 +7,17 @@
 from azure.durable_functions.orchestrator import Orchestrator
 from azure.durable_functions import DurableOrchestrationClient
 from typing import Union
-from azure.functions import FunctionRegister, TriggerApi, BindingApi, AuthLevel, SettingsApi
+from azure.functions import FunctionRegister, TriggerApi, BindingApi, AuthLevel
 from functools import wraps
 
+try:
+    from azure.functions import SettingsApi
+except ImportError:  # backwards compatibility path
+    class SettingsApi:
+        """Backwards compatibility mock of SettingsApi."""
+
+        pass
+
 
 class Blueprint(TriggerApi, BindingApi, SettingsApi):
     """Durable Functions (DF) Blueprint container.