Yes, i made it. Basically you have to save each IFormFile uploaded to a folder and store the paths as an array.

You can check my code, the result variable is what you have to store using forms api. First you check the type of the propertyValue and if IFormFile save it and get the path. Its very important to set the path right. There is a bug, if the path its not set right, when deleting the record it deletes the entire media folder. I reported the bug but i dont know if it is solved because i didnt get an answer :(

  var result = new List<object>();

            var tipo = propertyValue.GetType();
            if (tipo == typeof(StringValues))
            {
                var propertyValueSTR = propertyValue.ToString();
                if (propertyValueSTR == null) return result;
                result.Add(propertyValueSTR);
            }
            else if (tipo == typeof(List<IFormFile>))
            {
                var files = propertyValue as List<IFormFile>;
                if (files != null)
                {
                    foreach (var file in files)
                    {
                        if (file != null)
                        {
                            string uploadsFolder = string.Format(@"/media/forms/upload/form_{0}/{1}/{2}/", formId, recordKey, fieldKey);
                            var uploadsFolderAbs = this._helper.MapPath(uploadsFolder);
                            if (!Directory.Exists(uploadsFolderAbs))
                                Directory.CreateDirectory(uploadsFolderAbs);
                            var filePath = Path.Combine(uploadsFolder, file.FileName);
                            var filePathAbs = this._helper.MapPath(filePath);
                            if (System.IO.File.Exists(filePathAbs))
                                System.IO.File.Delete(filePathAbs);
                            using (Stream fileStream = new FileStream(filePathAbs, FileMode.Create))
                            {
                                file.CopyTo(fileStream);
                            }
                            result.Add(filePath);
                        }

                    }
                }

            }