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.
It's been there for a while I moved it to a comment as part of my previous commit (but I don't use it in this one and the comment is no longer accurate, so perhaps I should move it back)

The alerts stuff is very much tacked on and hardcoded for the UI parts.  I'm not a fan, but I don't see a better way without a lot of work.