public static string ImportUsers(InstagraphContext context, string jsonString)
        {
            var userDtos = JsonConvert.DeserializeObject<UserDto[]>(jsonString);
            var users = new List<User>();

            var builder = new StringBuilder();

            foreach (var dto in userDtos)
            {
                bool hasValidPic = context.Pictures.Any(x => x.Path == dto.ProfilePicture)
                    && !string.IsNullOrWhiteSpace(dto.ProfilePicture);
                bool hasValidName = !string.IsNullOrWhiteSpace(dto.Username)
                    && dto.Username.Length < 31 && !users.Any(x => x.Username == dto.Username);
                bool hasValidPass = !string.IsNullOrWhiteSpace(dto.Password)
                    && dto.Password.Length < 21;


                if (!hasValidPic || !hasValidName || !hasValidPass)
                {
                    builder.AppendLine(errorMsg);
                    continue;
                }
                var profilePicture = context.Pictures.SingleOrDefault(x => x.Path == dto.ProfilePicture);

                var user = Mapper.Map<User>(dto);
                user.ProfilePicture = profilePicture;
                users.Add(user);
                builder.AppendLine(string.Format(successMsg, $"User {user.Username}"));
            }
            context.Users.AddRange(users);
            context.SaveChanges();

            var result = builder.ToString().TrimEnd();
            return result;
        }