[python-nextgen] better datetime support in parameters (#14621)

* add allowStringInDateTimeParameters option

* add tests

* add files

* add tests for datetime query parameters

* fix file anme

* trigger build

* fix pytest

* install test requirement

* trigger build

* break build

* add new files

* fix Locale.ROOT

* update doc

.github/workflows/samples-python-nextgen-client-echo-api.yaml

@@ -0,0 +1,38 @@
+name: Python Client (Echo API)
+
+on:
+  push:
+    paths:
+      - samples/client/echo_api/python-nextgen/**
+  pull_request:
+    paths:
+      - samples/client/echo_api/python-nextgen/**
+jobs:
+  build:
+    name: Test Python client
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        sample:
+          # clients
+          - samples/client/echo_api/python-nextgen
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v4
+        with:
+          python-version: '3.7'
+      - name: Setup node.js
+        uses: actions/setup-node@v3
+      - name: Run echo server
+        run: |
+          git clone https://github.com/wing328/http-echo-server -b openapi-generator-test-server
+          (cd http-echo-server && npm install && npm start &)
+      - name: Install 
+        working-directory: ${{ matrix.sample }}
+        run: |
+          pip install -r requirements.txt
+          pip install -r test-requirements.txt
+      - name: Test
+        working-directory: ${{ matrix.sample }}
+        run: python -m pytest