add open orders and margin balance history API

Author: revilwang

README.md

@@ -0,0 +1,15 @@
+# MarginAccountBook
+
+## Properties
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+**id** | **str** | Balance change record ID | [optional] 
+**time** | **str** | Balance changed timestamp | [optional] 
+**currency** | **str** | Currency changed | [optional] 
+**currency_pair** | **str** | Account currency pair | [optional] 
+**change** | **str** | Amount changed. Positive value means transferring in, while negative out | [optional] 
+**balance** | **str** | Balance after change | [optional] 
+
+[[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
+
+

docs/DeliveryApi.md

@@ -0,0 +1,12 @@
+# OpenOrders
+
+## Properties
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+**currency_pair** | **str** | Currency pair | [optional] 
+**total** | **int** | Total open orders in this currency pair | [optional] 
+**orders** | [**list[Order]**](Order.md) |  | [optional] 
+
+[[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
+
+