This change forces us to use nested attributes for translations, instead
of using the more convenient `:"title_#{locale}"` methods.
On the other hand, we can use Rails' native `_destroy` attribute to
remove existing translations, so we don't have to use our custom
`delete_translations`, which was a bit buggy since it didn't consider
failed updates.
Using `have_content` detected textareas, but not text input contents.
All credit to Marko (mlovic) for finding the issue and suggesting the
implemented solution.
