message: add in link to the dynamodb book
diff: @@ -15,6 +15,8 @@ export class TheSagaStepfunctionSingleTableStack extends cdk.Stack {
  *
  * We store Flight, Hotel and Rental Car bookings in the same table.
  *
  + * For more help with single table DB structures see - https://www.dynamodbbook.com/
  + *
  * pk - the trip_id e.g. 1234
  * sk - bookingtype#booking_id e.g. HOTEL#345634, FLIGHT#574576, PAYMENT#45245
  */
  