CreateBookWithNotification.cs

        [HttpPost("Create")]
        public async Task<IActionResult> CreateBook(AddBookRequest request)
        {
            var command = await _mediator.Send(request);

            if (command)
            {
                await _mediator.Publish(new EmailNotification("admin@site.com", "A New Book Was Added"));

                return Ok();
            }
            return BadRequest();
        }