Retrieve the custom field definitions for a record type, including each field's type and choices. The field ids returned here are the keys used when filtering by custom fields. Valid record types are: people, businesses, events, smallgroups, group_members, group_types, forms, form_fields, connections, connection_types, locations, ministries, series, sermons, resource_rooms, resource_items, transaction_batch and safeguard_types. The required permission depends on the record type: people requires Limited Read People; smallgroups, group_members and group_types require Full Read Groups; connections and connection_types require Full Read Connections; businesses and transaction_batch require Limited Read Contributions; events requires Full Read Events; forms and form_fields require Full Read Forms; resource_rooms and resource_items require Full Read Facilities; safeguard_types requires Read Safeguards; the remaining record types require no specific permission.