removed pkg_resources dependency and added unit tests for the fix

Author: sunnywu

tests/test_request_response_util.py

@@ -0,0 +1,30 @@
+import unittest
+from unittest.mock import patch
+from importlib.metadata import version, PackageNotFoundError
+
+from uid2_client.request_response_util import auth_headers
+
+
+class TestRequestResponseUtil(unittest.TestCase):
+
+    def test_auth_headers_packaged_mode(self):
+        """Test that the version is correctly retrieved in packaged mode."""
+        try:
+            # In a test environment, the package might not be fully installed.
+            # We get the version directly if available.
+            expected_version = version("uid2_client")
+        except PackageNotFoundError:
+            # If not found, we can't run this specific check, so we skip it.
+            self.skipTest("uid2_client package not found, skipping packaged mode test.")
+
+        headers = auth_headers("test_auth_key")
+        self.assertEqual(headers['Authorization'], 'Bearer test_auth_key')
+        self.assertEqual(headers['X-UID2-Client-Version'], f"uid2-client-python-{expected_version}")
+
+    @patch('uid2_client.request_response_util.metadata.version')
+    def test_auth_headers_non_packaged_mode(self, mock_version):
+        """Test that the version is set to non-packaged-mode when the package is not found."""
+        mock_version.side_effect = PackageNotFoundError
+        headers = auth_headers("test_auth_key")
+        self.assertEqual(headers['Authorization'], 'Bearer test_auth_key')
+        self.assertEqual(headers['X-UID2-Client-Version'], "uid2-client-python-non-packaged-mode")