[
  { _id: 1, name: 'John'},
  { _id: 2, name: 'Sarah'}
]

[
  { uid: 1, paid: true },
  { uid: 2, paid: false }
]

[
  { user: { _id: 1, name: 'John' }, paid: true },
  { user: { _id: 2, name: 'Sarah' }, paid: false }
]