refactor: update version references to use standardized __version__

- Update ipinfo/handler_utils.py to use __version__ instead of SDK_VERSION
- Remove legacy version imports in setup.py to follow PEP 517
- Ensure User-Agent strings reflect the standardized version attribute
- Align internal API with PEP 396 module versioning conventions

Author: abstract-333

ipinfo/handler_utils.py

@@ -7,7 +7,7 @@
 import os
 import sys
 
-from .version import SDK_VERSION
+from .version import __version__ as SDK_VERSION
 
 # Base URL to make requests against.
 API_URL = "https://ipinfo.io"

ipinfo/version.py

@@ -1 +1 @@
-SDK_VERSION = "5.4.1"
+__version__ = "5.4.1"

setup.py

@@ -1,6 +1,6 @@
 from setuptools import setup
 
-from ipinfo.version import SDK_VERSION
+from ipinfo.version import __version__ as SDK_VERSION
 
 long_description = """
 The official Python library for IPinfo.