Get the leaderboard for a multiplayer room

curl --request GET \
  --url http://localhost:8787/api/v1/quiz-submissions/multiplayer/{roomId}/leaderboard

{
  "leaderboard": [
    {
      "userName": "<string>",
      "userId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
      "score": 123,
      "correctAnswers": 123,
      "avgTimeTaken": 123,
      "totalQuestions": 123,
      "questions": [
        {
          "text": "<string>",
          "correctAnswer": "<string>",
          "userAnswer": "<string>",
          "timeTaken": 123
        }
      ]
    }
  ]
}