[Java] Threetenbp dates support (#4029)

* [feign] add threetenbp support for feign clients

* [okhttp] add threetenbp support for okhttp clients

* [jersey] add threetenbp support for jersey clients

* [retrofit2] add threetenbp support for retrofit2 clients

* [spring] add threetenbp support for spring generators

* add a workaround in tests for a bug in the petstore

The petstore doesn't manage fractional digits of dates correctly when there are less than 3

samples/client/petstore/java/okhttp-gson/docs/FakeApi.md

@@ -88,7 +88,7 @@ Float _float = 3.4F; // Float | None
 String string = "string_example"; // String | None
 byte[] binary = B; // byte[] | None
 LocalDate date = new LocalDate(); // LocalDate | None
-DateTime dateTime = new DateTime(); // DateTime | None
+OffsetDateTime dateTime = new OffsetDateTime(); // OffsetDateTime | None
 String password = "password_example"; // String | None
 String paramCallback = "paramCallback_example"; // String | None
 try {
@@ -114,7 +114,7 @@ Name | Type | Description  | Notes
  **string** | **String**| None | [optional]
  **binary** | **byte[]**| None | [optional]
  **date** | **LocalDate**| None | [optional]
- **dateTime** | **DateTime**| None | [optional]
+ **dateTime** | **OffsetDateTime**| None | [optional]
  **password** | **String**| None | [optional]
  **paramCallback** | **String**| None | [optional]
 

samples/client/petstore/java/okhttp-gson/docs/FakeclassnametagsApi.md

@@ -0,0 +1,52 @@
+# FakeclassnametagsApi
+
+All URIs are relative to *http://petstore.swagger.io/v2*
+
+Method | HTTP request | Description
+------------- | ------------- | -------------
+[**testClassname**](FakeclassnametagsApi.md#testClassname) | **PATCH** /fake_classname_test | To test class name in snake case
+
+
+<a name="testClassname"></a>
+# **testClassname**
+> Client testClassname(body)
+
+To test class name in snake case
+
+### Example
+```java
+// Import classes:
+//import io.swagger.client.ApiException;
+//import io.swagger.client.api.FakeclassnametagsApi;
+
+
+FakeclassnametagsApi apiInstance = new FakeclassnametagsApi();
+Client body = new Client(); // Client | client model
+try {
+    Client result = apiInstance.testClassname(body);
+    System.out.println(result);
+} catch (ApiException e) {
+    System.err.println("Exception when calling FakeclassnametagsApi#testClassname");
+    e.printStackTrace();
+}
+```
+
+### Parameters
+
+Name | Type | Description  | Notes
+------------- | ------------- | ------------- | -------------
+ **body** | [**Client**](Client.md)| client model |
+
+### Return type
+
+[**Client**](Client.md)
+
+### Authorization
+
+No authorization required
+
+### HTTP request headers
+
+ - **Content-Type**: application/json
+ - **Accept**: application/json
+

samples/client/petstore/java/okhttp-gson/docs/FormatTest.md

@@ -14,7 +14,7 @@ Name | Type | Description | Notes
 **_byte** | **byte[]** |  | 
 **binary** | **byte[]** |  |  [optional]
 **date** | [**LocalDate**](LocalDate.md) |  | 
-**dateTime** | [**DateTime**](DateTime.md) |  |  [optional]
+**dateTime** | [**OffsetDateTime**](OffsetDateTime.md) |  |  [optional]
 **uuid** | [**UUID**](UUID.md) |  |  [optional]
 **password** | **String** |  | 
 

samples/client/petstore/java/okhttp-gson/docs/MixedPropertiesAndAdditionalPropertiesClass.md

@@ -5,7 +5,7 @@
 Name | Type | Description | Notes
 ------------ | ------------- | ------------- | -------------
 **uuid** | [**UUID**](UUID.md) |  |  [optional]
-**dateTime** | [**DateTime**](DateTime.md) |  |  [optional]
+**dateTime** | [**OffsetDateTime**](OffsetDateTime.md) |  |  [optional]
 **map** | [**Map<String, Animal>**](Animal.md) |  |  [optional]
 
 

samples/client/petstore/java/okhttp-gson/docs/Order.md

@@ -7,7 +7,7 @@ Name | Type | Description | Notes
 **id** | **Long** |  |  [optional]
 **petId** | **Long** |  |  [optional]
 **quantity** | **Integer** |  |  [optional]
-**shipDate** | [**DateTime**](DateTime.md) |  |  [optional]
+**shipDate** | [**OffsetDateTime**](OffsetDateTime.md) |  |  [optional]
 **status** | [**StatusEnum**](#StatusEnum) | Order Status |  [optional]
 **complete** | **Boolean** |  |  [optional]