Fix camelize special case

Author: gripep

drf_simple_api_errors/utils.py

@@ -29,7 +29,7 @@ def underscore_to_camel(match: re.Match) -> str:
         if len(group) == 3:
             return group[0] + group[2].upper()
         else:
-            return group[1].upper()
+            return group
 
     if not api_settings.CAMELIZE:
         return s

tests/test_utils.py

@@ -15,8 +15,8 @@ class TestCamelize:
             ("family_tree_name", "familyTreeName"),
             ("very_long_last_name_and_first_name", "veryLongLastNameAndFirstName"),
             # This is a special case where the underscore is at the start
-            # and should be removed, and the next character should be capitalized.
-            ("_special", "Special"),
+            # and should NOT be removed.
+            ("_special", "_special"),
         ],
     )
     def test_with_camelize_settings_true(self, mocker, field_input, expected_output):