Translatable::updateCMSFields

If the record is not shown in the default language, this method will try to autoselect a master language which is shown alongside the normal formfields as a readonly representation.

This gives translators a powerful tool for their translation workflow without leaving the translated page interface. Translatable also adds a new tab "Translation" which shows existing translations, as well as a formaction to create new translations based on a dropdown with available languages. This method can be called multiple times on the same FieldList because it checks which fields have already been added or modified.