python: copy the current Python generator into a "pydantic v1" generator (#16656)

* Copy the current Python generator into a "pydantic v1" generator

This generator will be deprecated over time and the normal generator will
focus on Pydantic v2.

* add missing doc

samples/client/echo_api/python-pydantic-v1/docs/AuthApi.md

@@ -0,0 +1,82 @@
+# openapi_client.AuthApi
+
+All URIs are relative to *http://localhost:3000*
+
+Method | HTTP request | Description
+------------- | ------------- | -------------
+[**test_auth_http_basic**](AuthApi.md#test_auth_http_basic) | **POST** /auth/http/basic | To test HTTP basic authentication
+
+
+# **test_auth_http_basic**
+> str test_auth_http_basic()
+
+To test HTTP basic authentication
+
+To test HTTP basic authentication
+
+### Example
+
+* Basic Authentication (http_auth):
+```python
+import time
+import os
+import openapi_client
+from openapi_client.rest import ApiException
+from pprint import pprint
+
+# Defining the host is optional and defaults to http://localhost:3000
+# See configuration.py for a list of all supported configuration parameters.
+configuration = openapi_client.Configuration(
+    host = "http://localhost:3000"
+)
+
+# The client must configure the authentication and authorization parameters
+# in accordance with the API server security policy.
+# Examples for each auth method are provided below, use the example that
+# satisfies your auth use case.
+
+# Configure HTTP basic authorization: http_auth
+configuration = openapi_client.Configuration(
+    username = os.environ["USERNAME"],
+    password = os.environ["PASSWORD"]
+)
+
+# Enter a context with an instance of the API client
+with openapi_client.ApiClient(configuration) as api_client:
+    # Create an instance of the API class
+    api_instance = openapi_client.AuthApi(api_client)
+
+    try:
+        # To test HTTP basic authentication
+        api_response = api_instance.test_auth_http_basic()
+        print("The response of AuthApi->test_auth_http_basic:\n")
+        pprint(api_response)
+    except Exception as e:
+        print("Exception when calling AuthApi->test_auth_http_basic: %s\n" % e)
+```
+
+
+
+### Parameters
+This endpoint does not need any parameter.
+
+### Return type
+
+**str**
+
+### 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 |  -  |
+
+[[Back to top]](#) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to Model list]](../README.md#documentation-for-models) [[Back to README]](../README.md)
+