Feat: Delegated Auth

[nelsonic]

Imagine you're building an App that allows small children to manage their own Task List & Calendar
We want the child to be able to authenticate with their email/OAuth account and use the App.
But then we also want the parent to be able to access the data.
This can easily be done with the concept of Groups #232 ...
where the parent would "own" the group and the child would be a member of the group.
But then how do we inform the App of this relationship? 💭

Google already has this with "Family Link": https://support.google.com/families/answer/7103262?hl=en

At present I don't have a fully-formed idea of what this will look like; this is a place-holder issue.
But I've been thinking about how to setup an App in which a Parent or Guardian has visibility of what their child is doing.