public IHttpActionResult PostQuotation(Quotation quotation)
        {
            // TODO: DB的には必須だけど、リクエスト的には不要な場合ってどうすればいいのかな
            //if (!ModelState.IsValid)
            //{
            //    return BadRequest(ModelState);
            //}

            quotation.CreatedAt = DateTime.Now;
            quotation.UpdatedAt = DateTime.Now;

            db.Quotations.Add(quotation);
            db.SaveChanges();

            return CreatedAtRoute("DefaultApi", new { id = quotation.Id }, quotation);
        }
        public IHttpActionResult PutQuotation(int id, Quotation quotation)
        {
            if (!ModelState.IsValid)
            {
                return BadRequest(ModelState);
            }

            if (id != quotation.Id)
            {
                return BadRequest();
            }

            quotation.UpdatedAt = DateTime.Now;

            db.Entry(quotation).State = EntityState.Modified;

            try
            {
                db.SaveChanges();
            }
            catch (DbUpdateConcurrencyException)
            {
                if (!QuotationExists(id))
                {
                    return NotFound();
                }
                else
                {
                    throw;
                }
            }

            return StatusCode(HttpStatusCode.NoContent);
        }