When a page is delivered through an external translation service, we still want to provide a way to contribute (T212300). After explaining the different options, users can jump to editing. When doing such transition we want to make sure that:

• Users access Visual Editor, using the visual mode as the default (if they have no preference indicating otherwise). This is the current situation on desktop, but we want to make sure that the visual mode is also accessed by default on mobile.
• A campaign parameter with the value external-machine-translation is passed to Visual Editor to make the tool aware that contributions are made based on an automatic page translation, to facilitate review of such content (check T209132 for more details about how this parameter works).