Return stewardship w/ default mobile fields

Because this is adding a new type of field group that the mobile do not
have the ability to render yet, these changes are only available in v3 of
the API.

This is intended to be the final feature in v3, and all new breaking
changes should be part of v4.
Is it now a problem that we mention ``'Alerts'`` here, but alerts will not be a default field for every instance.