updated history

sdk/iothub/azure-mgmt-iothub/HISTORY.rst

@@ -10,6 +10,18 @@ Release History
 
 - Model IotHubProperties has a new parameter locations
 
+**General breaking changes**  
+
+This version uses a next-generation code generator that *might* introduce breaking changes if from some import.
+In summary, some modules were incorrectly visible/importable and have been renamed. This fixed several issues caused by usage of classes that were not supposed to be used in the first place.
+
+- IotHubClient cannot be imported from `azure.mgmt.iothub.iot_hub_client` anymore (import from `azure.mgmt.iothub` works like before)
+- IotHubClientConfiguration import has been moved from `azure.mgmt.iothub.iot_hub_client` to `azure.mgmt.iothub`
+- A model `MyClass` from a "models" sub-module cannot be imported anymore using `azure.mgmt.iothub.models.my_class` (import from `azure.mgmt.iothub.models` works like before)
+- An operation class `MyClassOperations` from an `operations` sub-module cannot be imported anymore using `azure.mgmt.iothub.operations.my_class_operations` (import from `azure.mgmt.iothub.operations` works like before)
+
+Last but not least, HTTP connection pooling is now enabled by default. You should always use a client as a context manager, or call close(), or use no more than one client per process.
+
 0.8.2 (2019-05-15)
 ++++++++++++++++++