[#5074] Use camel_to_underscore from the library instead of re-implem…

…enting this

src/openforms/api/utils.py

@@ -23,13 +23,6 @@ def underscore_to_camel(input_: str | int) -> str:
     return re.sub(camelize_re, _underscore_to_camel, input_)
 
 
-def camel_to_underscore(input: str) -> str:
-    """
-    Convert a string from camelCase to snake_case
-    """
-    return re.sub(r"(?<!^)(?=[A-Z])", "_", input).lower()
-
-
 def get_from_serializer_data_or_instance(
     field: str, data: Mapping, serializer: Serializer
 ) -> Any:

src/openforms/registrations/contrib/json_dump/plugin.py

@@ -9,9 +9,9 @@
 from django.db.models.functions import Coalesce, NullIf
 from django.utils.translation import gettext_lazy as _
 
+from djangorestframework_camel_case.util import camel_to_underscore
 from zgw_consumers.client import build_client
 
-from openforms.api.utils import camel_to_underscore
 from openforms.formio.constants import DataSrcOptions
 from openforms.formio.service import rewrite_formio_components
 from openforms.formio.typing import (

src/openforms/registrations/contrib/objects_api/handlers/v2.py

@@ -7,9 +7,10 @@
 from datetime import date, datetime
 from typing import assert_never, cast
 
+from djangorestframework_camel_case.util import camel_to_underscore
 from glom import Assign, Path, glom
 
-from openforms.api.utils import camel_to_underscore, underscore_to_camel
+from openforms.api.utils import underscore_to_camel
 from openforms.formio.service import FormioData
 from openforms.formio.typing import Component, EditGridComponent
 from openforms.formio.typing.vanilla import FileComponent