fix(scim): keep lists of plain values flat in snake_cased_body

_convert_dict_keys appended a copy of the whole list for every element of a
list that does not hold dicts, so a value like schemas: ["a", "b"] became
[["a", "b"], ["a", "b"]]. Append a copy of each element instead.

Author: kwy404

slack_sdk/scim/v1/internal_utils.py

@@ -108,7 +108,7 @@ def _convert_dict_keys(
                             )
                         result_dict[new_key].append(new_element)
                 else:
-                    result_dict[new_key].append(_create_copy(original_value))
+                    result_dict[new_key].append(_create_copy(element))
         else:
             result_dict[new_key] = _create_copy(original_value)
     return result_dict

tests/slack_sdk/scim/test_internals.py

@@ -16,3 +16,7 @@ def test_snake_cased(self):
         result = _to_snake_cased(json.loads(response_body))
         self.assertEqual(result["start_index"], 1)
         self.assertIsNotNone(result["resources"][0]["id"])
+
+    def test_snake_cased_list_of_plain_values(self):
+        result = _to_snake_cased({"schemas": ["urn:scim:schemas:core:1.0", "urn:scim:schemas:extension:enterprise:1.0"]})
+        self.assertEqual(result["schemas"], ["urn:scim:schemas:core:1.0", "urn:scim:schemas:extension:enterprise:1.0"])