The same way we did for banners.
We needed to add new translation keys so the labels are displayed in the
correct language. I've kept the original `title` and `body` attributes
so they can be used in other places.
While backporting, we also added the original translations because they
hadn't been backported yet.
In Madrid, the button text didn't change depending on whether the form
is for the "new" page or for the "edit" page.
In consul, the buttons texts were "create admin notification" and
"update admin notification" instead of "create notification" and "update
notification".
Also change translation key from "submit" to "submit_button" to
match other instances.
In the same fashion Newsletters is managed, with the only difference that
the preview is using the notification partial in the same way the index
of notifications.
