fix: make pylint conditional to maintain Python 3.9 compatibility

- Add conditional pylint installation in [project.optional-dependencies]
  - Python 3.10+: pylint >=4.0.0
  - Python 3.9: pylint >=2.0, <4.0
- Remove hardcoded pylint from [tool.poetry.dev-dependencies]
- Maintains backwards compatibility with Python 3.9 while allowing
  Python 3.10+ users to use pylint v4

Fixes Python 3.9 CI/CD compatibility issue with pylint v4 upgrade.
This PR builds on top of PR #133 (pylint v4 upgrade) and adds
Python 3.9 compatibility.

Author: BrandtKruger

pyproject.toml

@@ -46,6 +46,21 @@ fastapi = [
 flask = [
     "flask >=3.0.0, <4.0.0",
 ]
+dev = [
+    "pytest >=7.4.0",
+    "pytest-cov >=4.1.0",
+    "pytest-django >=4.5.2",
+    "mypy >=1.5.0",
+    "bandit >=1.7",
+    "pylint >=4.0.0; python_version >= '3.10'",
+    "pylint >=2.0, <4.0; python_version < '3.10'",
+    "pycodestyle >=2.0",
+    "pytest-asyncio >=0.26.0",
+    "pytest-timeout >=2.2.0",
+    "black >=24.3.0",
+    "flake8 >=6.1.0",
+    "isort >=5.12.0",
+]
 
 [project.urls]
 "Homepage" = "https://github.com/kinde-oss/kinde-python-sdk"
@@ -71,7 +86,10 @@ pytest-cov = "^4.1.0"
 pytest-django = "^4.5.2"
 mypy = "^1.5.0"
 bandit = "^1.7"
-pylint = "^4.0.0"
+# pylint is now conditionally installed based on Python version
+# Python 3.10+: pylint >=4.0.0
+# Python 3.9: pylint >=2.0, <4.0
+# Install via: pip install -e ".[dev]"
 pycodestyle = "^2.0"
 pytest-asyncio = "^0.26.0"
 pytest-timeout = "^2.2.0"