public IResult AddDeveloper(string developerName, string developerLastname, string username, List <int> categoryIds)
        {
            List <Category> categories = new List <Category>();

            foreach (int categoryId in categoryIds)
            {
                Category cat = DbInstance.GetCategoryById(categoryId);
                categories.Add(cat);
            }
            Developer developer = new Developer
            {
                Categories  = categories,
                CreatedDate = DateTime.Now,
                FirstName   = developerName,
                LastName    = developerLastname,
                UserName    = username,
            };

            try
            {
                DbInstance.AddDeveloper(developer);
                DbInstance.SaveChanges();
                return(new SuccessResult(Messages.SuccessAddDeveloper));
            }
            catch (Exception)
            {
                return(new ErrorResult(Messages.ErrorAddDeveloper));
            }
        }