public async Task <Comment> AddComment(string photoId, string albumId, string message, User requestor)
        {
            if (!await _permissionsService.CanComment(requestor, albumId))
            {
                return(null);
            }
            var photo = await _photoService.GetPhoto(photoId);

            var comment = new Comment
            {
                ReactionId   = _guid.NewGuid().ToString(),
                Text         = message,
                Reactor      = requestor,
                ReactionDate = _clock.UtcNow
            };
            var photoComment = new PhotoComment
            {
                Photo   = photo,
                Comment = comment
            };

            photo.PhotoComments.Add(photoComment);
            await _unitOfWork.Photos.Update(photo);

            return(comment);
        }