Returns the custom field definitions the library configured for compliance tasks. The response is a plain list:
it is bounded by the library's configuration, so it is not paginated.

An occurrence reports only slug, name, required and value per custom field. The field type and its allowed
values are read from here, and
Save Task Occurrence takes the values keyed by the
same slug.

options holds the allowed values of a choices or multi field. It is an empty array when the field is of one
of those types but no values were configured yet, and null for the types that carry no option list at all.

The possible values of type are listed on the
Reference Values page.