Convert the "owners" array to User objects
When an app needs to display the name(s) of the owner(s) of a Collection or Fragment, it currently has to make a separate request for each user object.
This is easy to solve with GraphQL, but for the REST API perhaps we could automatically convert the owners
array from ids to User objects?
The workaround is to repeatedly load every user into the client's redux store, or to make a separate request for each user, neither of which is ideal.