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/openapi3/client/petstore/python-pydantic-v1/setup.py

@@ -0,0 +1,52 @@
+# coding: utf-8
+
+"""
+    OpenAPI Petstore
+
+    This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+
+    The version of the OpenAPI document: 1.0.0
+    Generated by OpenAPI Generator (https://openapi-generator.tech)
+
+    Do not edit the class manually.
+"""  # noqa: E501
+
+
+from setuptools import setup, find_packages  # noqa: H301
+
+# To install the library, run the following
+#
+# python setup.py install
+#
+# prerequisite: setuptools
+# http://pypi.python.org/pypi/setuptools
+NAME = "petstore-api"
+VERSION = "1.0.0"
+PYTHON_REQUIRES = ">=3.7"
+REQUIRES = [
+    "urllib3 >= 1.25.3, < 2.1.0",
+    "python-dateutil",
+    "pem>=19.3.0",
+    "pycryptodome>=3.9.0",
+    "pydantic >= 1.10.5, < 2",
+    "aenum"
+]
+
+setup(
+    name=NAME,
+    version=VERSION,
+    description="OpenAPI Petstore",
+    author="OpenAPI Generator community",
+    author_email="team@openapitools.org",
+    url="",
+    keywords=["OpenAPI", "OpenAPI-Generator", "OpenAPI Petstore"],
+    install_requires=REQUIRES,
+    packages=find_packages(exclude=["test", "tests"]),
+    include_package_data=True,
+    license="Apache-2.0",
+    long_description_content_type='text/markdown',
+    long_description="""\
+    This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \&quot; \\
+    """,  # noqa: E501
+    package_data={"petstore_api": ["py.typed"]},
+)