Changes to List custom field definitions

added the optional property code to the response with the 400 status

added the optional property code to the response with the 401 status

added the optional property code to the response with the 403 status

added the optional property code to the response with the 404 status

added the optional property code to the response with the 500 status

added the new Extension enum value to the items/schema/oneOf[subschema #10: CustomFieldResourceReferenceSchema]/allowed_types/items response property for the response status 200

added the new Extension enum value to the items/scope_type response property for the response status 200

added the new Extension enum value to the items/target_type response property for the response status 200

added the new enum value Extension to the query request parameter scope_type

added the new enum value Extension to the query request parameter target_type

endpoint added