useFirestoreConnect with populates - usage/implementation

DB Setup:

- users
  - A: { // private user info }
- usersPublic
  - A: { // public user info }
- rooms
  - 1: { readAccess: ['A'] }

I have a component that displays all rooms and am fetching that in the following way:

useFirestoreConnect(() => [{collection: 'rooms'}] )

This is working fine, but I now want to also load in the info from usersPublic for each user in the rooms readAccess array.

I'm attempting to use populates in the following way:

useFirestoreConnect(() => [{
  collection: 'rooms',
  populates: [{
    root: 'usersPublic',
    child: 'A'
  }]
}])

I'm pretty sure my implementation of populates is wrong and I'm failing to understand exactly how to make this work.

I could return a bunch of other query configs for all users with read access once I have the room object but that seems inefficient and it seems that populates is meant to solve exactly this problem.

I'm also open to suggestions on modeling the DB structure - the above made sense to me and offers a nice separation between private/public user info but there might be a better way.

The way to do it is:

populates: [{ root: usersPublic, child: 'read_access ' }]

This results in a redux state that looks like:

...etc
data: {
  rooms: { ... rooms ... }
  usersPublic: { A: { ... usersPublic[A] ... }, etc }
}