public IActionResult CreateDocument(int schoolId, int courseId,
                                            [FromBody] DocumentDTO documentDTO)
        {
            if (!ModelState.IsValid)
            {
                return(BadRequest(ModelState));
            }
            Document document = new Document()
            {
                Name = documentDTO.Name,
                Link = documentDTO.Link
            };

            _schoolRepository.AddDocument(document, schoolId, courseId);
            return(CreatedAtRoute("GetDocument", new { schoolId, courseId, documentId = document.Id }, document));
        }