Interface for element type that supports multiple fields.
File: src/db-objects/elements/element-types/multi-field-element-type-interface.php
Multi_Field_Element_Type_Interface::get_additional_field_slugs()
Returns the slugs for the additional fields of this type.
Multi_Field_Element_Type_Interface::additional_fields_to_json()
Returns an array representation for each additional field of an element.
Multi_Field_Element_Type_Interface::validate_additional_fields()
Validates additional fields for an element.