Add a new Python client generator - python-nextgen (#14157)

* add python-nextgen generator

* remove client_side_validation from model

* remove configuraiton import from models

* add inheritance support

* update test requirements, tox

* add typings, pydanic to models

* add test model

* minor improvements

* add enum support

* add typing for parameters, remove validations

* add oneof, anyof support

* fix default value

* fix deserialization, api tests passed

* private variable naming, update tests, all tests passed

* remove six

* remove nose

* update doc

* remove sortParamsByRequiredFlag option

* add parameter validation

* add validation tests

* simplify Field()

* remove previous required parameter validation

* improve parameter handling

* support discriminator mapping

* better typing discriminator mapping

* format test code

* fix tests

* fix oneOf from_dict, add test

* add set validation test

* fix nested oneof serialization, add tests

* add model import

* remove models. prefix

* remove import models

* remove model import from api

* simplify from_dict

* add typing for return

* skip pydantic import in return type

* fix tests, fix enum

* restore more enum schema tests

* uncomment enum integer test

* clean up getfullargspec import in model

* clean up getfullargspec import

* fix deserilizatoin for nested oneof

* minor fixes, add tests

* fix regular expression

* add aiohttp samples, add tests

* remove default content type to json

* update template

* fix select accept, content-type

* move tests

* move tests

* fix url query parameters

* fix list

* fix samples

* fix param pydantic, add list as reserved word

* fix auto-generated doc

* fix readme

* fix list, fix special variable name with var_

* fix Literal in python 3.7

* fix default configuration

* fix aiohttp tests

* set default api client instance

* deprecate get_default_copy method

* fix enum model

* fix enum serializatio/deserialization

* add github workflow support

* add regular expression validator

* add enum validator

* better model import

* fix file, remove x-py-import-models

* rename local var

* better model example

* fix regular expression warning, add special_name test, whitelist schema

* skip self import

* update samples

* various fixes

* add base64, json as reserved word

* add http signature support

* add http signature test

* add additioanl properties support in python client

* add decimal support

* use strictstr instead of constr

* fix test with virtualenv

* add nullable support

* add readonly support

* add model name caching

* fix circular reference import

* add onelook discriminator lookup

* add tests

* update samples

* fix locale

* Fix client legacy generator asyncio README code example

* test python-nextgen in circleci

* fix pom.xml

* update python to 3.7.15

* test with python 3.7.12

* various updates

* fix python legacy

samples/openapi3/client/petstore/python-nextgen/setup.py

@@ -0,0 +1,49 @@
+# 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: \" \\  # noqa: E501
+
+    The version of the OpenAPI document: 1.0.0
+    Generated by: https://openapi-generator.tech
+"""
+
+
+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",
+    "python-dateutil",
+    "pem>=19.3.0",
+    "pycryptodome>=3.9.0",
+    "pydantic",
+    "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: \" \\  # noqa: E501
+    """
+)