[python] Validate pyproject.toml and fix the pyproject.toml version constraint format (#21402)

* Validate pyproject.toml of echo client python sample

* Use PEP-508 compatible version constraint for `requires-python` key

* Update samples

* Move job to petstore workflow

* Update generated sample

* Use equals or greater than operator instead of greater than

* Update samples

.github/workflows/samples-python-petstore.yaml

@@ -8,6 +8,18 @@ on:
       - .github/workflows/samples-python-petstore.yaml
 
 jobs:
+  validate-pyproject-toml:
+    name: Validate pyproject.toml
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.13"
+      - name: Install validator
+        run: pip install 'validate-pyproject[all]'
+      - name: Validate
+        run: validate-pyproject samples/openapi3/client/petstore/python/pyproject.toml
   build:
     name: Test Python client
     runs-on: ubuntu-latest

modules/openapi-generator/src/main/resources/python/pyproject.mustache

@@ -43,7 +43,7 @@ pydantic = ">= 2"
 typing-extensions = ">= 4.7.1"
 {{/poetry1}}
 {{^poetry1}}
-requires-python = "^3.9"
+requires-python = ">=3.9"
 
 dependencies = [
   "urllib3 (>=2.1.0,<3.0.0)",

samples/client/echo_api/python-disallowAdditionalPropertiesIfNotPresent/pyproject.toml

@@ -8,7 +8,7 @@ authors = [
 license = "Apache 2.0"
 readme = "README.md"
 keywords = ["OpenAPI", "OpenAPI-Generator", "Echo Server API"]
-requires-python = "^3.9"
+requires-python = ">=3.9"
 
 dependencies = [
   "urllib3 (>=2.1.0,<3.0.0)",

samples/client/echo_api/python/pyproject.toml

@@ -8,7 +8,7 @@ authors = [
 license = "Apache 2.0"
 readme = "README.md"
 keywords = ["OpenAPI", "OpenAPI-Generator", "Echo Server API"]
-requires-python = "^3.9"
+requires-python = ">=3.9"
 
 dependencies = [
   "urllib3 (>=2.1.0,<3.0.0)",

samples/openapi3/client/petstore/python/pyproject.toml

@@ -8,7 +8,7 @@ authors = [
 license = "Apache-2.0"
 readme = "README.md"
 keywords = ["OpenAPI", "OpenAPI-Generator", "OpenAPI Petstore"]
-requires-python = "^3.9"
+requires-python = ">=3.9"
 
 dependencies = [
   "urllib3 (>=2.1.0,<3.0.0)",