/// <summary>
/// Add instance to database
/// </summary>
/// <param name="entity">new instance</param>
/// <returns>error message if error happaned, otherwise return instance</returns>
public virtual async Task <(T instance, string errorMessage)> AddAsync(T entity)
{
try
{
dbContext.Set <T>().Add(entity);
await dbContext.SaveChangesAsync();
return(entity, string.Empty);
}
catch (DbUpdateException e) { return(entity, e?.InnerException?.Message ?? e.Message); }
}