1. RETURN ONLY AUTHOR ID

{
  id: 1,
  title: 'best playlist ever',
  author: 12
}

---

2. RETURN ABBREVIATED AUTHOR CONTAINING ONLY ID

{
  id: 1,
  title: 'best playlist ever',
  author: {
    id: 12
  }
}

---

3. RETURN WHOLE AUTHOR

{
  id: 1,
  title: 'best playlist ever',
  author: {
    id: 12,
    some: 'other attribute',
    another: 'attribute'
  }
}