Add tests for http basic authentication in python client (#16488)

* add tests for http basic auth in python client

* add new files

samples/client/echo_api/java/apache-httpclient/docs/AuthApi.md

@@ -0,0 +1,77 @@
+# AuthApi
+
+All URIs are relative to *http://localhost:3000*
+
+| Method | HTTP request | Description |
+|------------- | ------------- | -------------|
+| [**testAuthHttpBasic**](AuthApi.md#testAuthHttpBasic) | **POST** /auth/http/basic | To test HTTP basic authentication |
+
+
+
+## testAuthHttpBasic
+
+> String testAuthHttpBasic()
+
+To test HTTP basic authentication
+
+To test HTTP basic authentication
+
+### Example
+
+```java
+// Import classes:
+import org.openapitools.client.ApiClient;
+import org.openapitools.client.ApiException;
+import org.openapitools.client.Configuration;
+import org.openapitools.client.auth.*;
+import org.openapitools.client.models.*;
+import org.openapitools.client.api.AuthApi;
+
+public class Example {
+    public static void main(String[] args) {
+        ApiClient defaultClient = Configuration.getDefaultApiClient();
+        defaultClient.setBasePath("http://localhost:3000");
+        
+        // Configure HTTP basic authorization: http_auth
+        HttpBasicAuth http_auth = (HttpBasicAuth) defaultClient.getAuthentication("http_auth");
+        http_auth.setUsername("YOUR USERNAME");
+        http_auth.setPassword("YOUR PASSWORD");
+
+        AuthApi apiInstance = new AuthApi(defaultClient);
+        try {
+            String result = apiInstance.testAuthHttpBasic();
+            System.out.println(result);
+        } catch (ApiException e) {
+            System.err.println("Exception when calling AuthApi#testAuthHttpBasic");
+            System.err.println("Status code: " + e.getCode());
+            System.err.println("Reason: " + e.getResponseBody());
+            System.err.println("Response headers: " + e.getResponseHeaders());
+            e.printStackTrace();
+        }
+    }
+}
+```
+
+### Parameters
+
+This endpoint does not need any parameter.
+
+### Return type
+
+**String**
+
+### Authorization
+
+[http_auth](../README.md#http_auth)
+
+### HTTP request headers
+
+- **Content-Type**: Not defined
+- **Accept**: text/plain
+
+
+### HTTP response details
+| Status code | Description | Response headers |
+|-------------|-------------|------------------|
+| **200** | Successful operation |  -  |
+