title: Firestore get documents with maximum value
body: <p>I have a collection of documents: </p>
  
  <pre><code>data class Game(
      var userId: String? = "",
      var userName: String? = "",
      var date: Timestamp? = null,
      var award: Int
  )
  </code></pre>
  
  <p>I want to make a rating for last week, ordered by the award and grouped by username (just 1 row for every user).</p>
  
  <p>This code returns all records with repetition. </p>
  
  <pre><code>db.collection("games").orderBy("award", Query.Direction.DESCENDING).limit(50).get()
  </code></pre>
  
  <p>Is any way to get users with maximum award value without repetition users? Or maybe my database structure is wrong?</p>