public UserService(IPOCDatabaseSettings settings)
        {
            var client   = new MongoClient(settings.ConnectionString);
            var database = client.GetDatabase(settings.DatabaseName);

            _users = database.GetCollection <User>(settings.UserCollectionName);
        }
        public DailyChallengeService(IPOCDatabaseSettings settings)
        {
            var client   = new MongoClient(settings.ConnectionString);
            var database = client.GetDatabase(settings.DatabaseName);

            _challenges = database.GetCollection <DailyChallenge>(settings.ChallengeCollectionName);
        }