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/FormApi.md

@@ -0,0 +1,156 @@
+# openapi_client.FormApi
+
+All URIs are relative to *http://localhost:3000*
+
+Method | HTTP request | Description
+------------- | ------------- | -------------
+[**test_form_integer_boolean_string**](FormApi.md#test_form_integer_boolean_string) | **POST** /form/integer/boolean/string | Test form parameter(s)
+[**test_form_oneof**](FormApi.md#test_form_oneof) | **POST** /form/oneof | Test form parameter(s) for oneOf schema
+
+
+# **test_form_integer_boolean_string**
+> str test_form_integer_boolean_string(integer_form=integer_form, boolean_form=boolean_form, string_form=string_form)
+
+Test form parameter(s)
+
+Test form parameter(s)
+
+### Example
+
+```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"
+)
+
+
+# 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.FormApi(api_client)
+    integer_form = 56 # int |  (optional)
+    boolean_form = True # bool |  (optional)
+    string_form = 'string_form_example' # str |  (optional)
+
+    try:
+        # Test form parameter(s)
+        api_response = api_instance.test_form_integer_boolean_string(integer_form=integer_form, boolean_form=boolean_form, string_form=string_form)
+        print("The response of FormApi->test_form_integer_boolean_string:\n")
+        pprint(api_response)
+    except Exception as e:
+        print("Exception when calling FormApi->test_form_integer_boolean_string: %s\n" % e)
+```
+
+
+
+### Parameters
+
+Name | Type | Description  | Notes
+------------- | ------------- | ------------- | -------------
+ **integer_form** | **int**|  | [optional] 
+ **boolean_form** | **bool**|  | [optional] 
+ **string_form** | **str**|  | [optional] 
+
+### Return type
+
+**str**
+
+### Authorization
+
+No authorization required
+
+### HTTP request headers
+
+ - **Content-Type**: application/x-www-form-urlencoded
+ - **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)
+
+# **test_form_oneof**
+> str test_form_oneof(form1=form1, form2=form2, form3=form3, form4=form4, id=id, name=name)
+
+Test form parameter(s) for oneOf schema
+
+Test form parameter(s) for oneOf schema
+
+### Example
+
+```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"
+)
+
+
+# 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.FormApi(api_client)
+    form1 = 'form1_example' # str |  (optional)
+    form2 = 56 # int |  (optional)
+    form3 = 'form3_example' # str |  (optional)
+    form4 = True # bool |  (optional)
+    id = 56 # int |  (optional)
+    name = 'name_example' # str |  (optional)
+
+    try:
+        # Test form parameter(s) for oneOf schema
+        api_response = api_instance.test_form_oneof(form1=form1, form2=form2, form3=form3, form4=form4, id=id, name=name)
+        print("The response of FormApi->test_form_oneof:\n")
+        pprint(api_response)
+    except Exception as e:
+        print("Exception when calling FormApi->test_form_oneof: %s\n" % e)
+```
+
+
+
+### Parameters
+
+Name | Type | Description  | Notes
+------------- | ------------- | ------------- | -------------
+ **form1** | **str**|  | [optional] 
+ **form2** | **int**|  | [optional] 
+ **form3** | **str**|  | [optional] 
+ **form4** | **bool**|  | [optional] 
+ **id** | **int**|  | [optional] 
+ **name** | **str**|  | [optional] 
+
+### Return type
+
+**str**
+
+### Authorization
+
+No authorization required
+
+### HTTP request headers
+
+ - **Content-Type**: application/x-www-form-urlencoded
+ - **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)
+