This class can be used to provide an interface for specifying internationalized text strings saved in message keys via input from a form. When editing the content provided via the input field is saved together with an item-specific message keys in the message key tables via lang::util::convert_to_i18n.
This formfield class is especially useful for xowiki items which have no language-prefix (e.g. folders or links). In other cases it is probably still a better idea to create same named pages with different language prefixes.