Dependent hooks

[nhagen]

Seems like a common flow I see for defining admin users is to have an admin collection, and then you can check the authenticated user against that collection to make a determination.

Since hooks can't show conditionally, the syntax for doing this seems to be along the lines of:

const { initializing, user } = useAuthState(auth);
const { loading, error, value } = useDocument(db.doc(`admins/${ user && user.email }`));
...
const isAdmin = !!value.exists;

In this case, we begin by querying via useDocument for a document we know won't work (admins/), but it of course works fine when user.email is available.

Is there a better way of doing this with hooks and firebase?

[nhagen]

Actually looks like this PR addresses this.
#10
Not sure if there more discussion to be had--that API seems fine.