chore: drop Python 3.9 support, add Python 3.13 (#843)

### Changes

- Drop Python 3.9 from supported versions (EOL since October 2025)
- Add Python 3.13 to the test matrix and classifiers
- Bump minimum Python version to `>=3.10` in `pyproject.toml`
- Update publish workflow to build on Python 3.10
- Unpin Poetry version constraint (Poetry 2.x requires Python 3.10+,
which is now our minimum)

This also fixes CI failures on PR #841 where `pipx install poetry` was
pulling Poetry 2.x which crashes on Python 3.9 with `TypeError:
dataclass() got an unexpected keyword argument 'slots'`.

### References

- [Poetry 2.0
changelog](https://python-poetry.org/blog/announcing-poetry-2.0.0/)
(requires Python 3.10+)
- [Python 3.9 EOL](https://devguide.python.org/versions/) (end-of-life
October 2025)

### Testing

- CI matrix now runs on Python 3.10, 3.11, 3.12, 3.13
- No code changes to the library itself, only build/CI configuration

- [ ] This change adds unit test coverage
- [x] This change has been tested on the latest version of the
platform/language or why not

### Checklist

- [x] I have read the [Auth0 general contribution
guidelines](https://github.com/auth0/open-source-template/blob/master/GENERAL-CONTRIBUTING.md)
- [x] I have read the [Auth0 Code of
Conduct](https://github.com/auth0/open-source-template/blob/master/CODE-OF-CONDUCT.md)
- [x] All existing and new tests complete without errors

Author: developerkunal

.github/workflows/publish.yml

@@ -102,7 +102,7 @@ jobs:
       - name: Configure Python
         uses: actions/setup-python@v6
         with:
-          python-version: "3.9"
+          python-version: "3.10"
 
       - name: Configure dependencies
         run: |

.github/workflows/test.yml

@@ -38,7 +38,7 @@ jobs:
 
     strategy:
       matrix:
-        python-version: ["3.9", "3.10", "3.11", "3.12"]
+        python-version: ["3.10", "3.11", "3.12", "3.13"]
 
     steps:
       - name: Checkout code

README.md

@@ -34,7 +34,7 @@ pip install auth0-python
 ```
 
 **Requirements:**
-- Python ≥3.9 (Python 3.8 support has been dropped)
+- Python ≥3.10 (Python 3.9 support has been dropped)
 
 ## Reference
 

poetry.lock

@@ -14,10 +14,10 @@ classifiers = [
     "Intended Audience :: Developers",
     "Programming Language :: Python",
     "Programming Language :: Python :: 3",
-    "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
+    "Programming Language :: Python :: 3.13",
     "Operating System :: OS Independent",
     "Operating System :: POSIX",
     "Operating System :: MacOS",
@@ -35,7 +35,7 @@ Repository = 'https://github.com/auth0/auth0-python'
 Homepage = 'https://auth0.com'
 
 [tool.poetry.dependencies]
-python = ">=3.9.2,<4.0"
+python = ">=3.10"
 httpx = ">=0.21.2"
 pydantic = ">= 1.9.2"
 pydantic-core = ">=2.18.2"