Get a Flash Price Campaign

The product price sets of this flash price campaigns.<br> 商品限時促銷價活動的商品限時價格。<br> Presented in GET/flash_price_campaigns{id}, POST/flash_price_campaigns, PUT/flash_price_campaigns{id} but not in GET/flash_price_campaigns.<br> 會於 GET/flash_price_campaigns{id}及POST/flash_price_campaigns及 PUT/flash_price_campaigns{id}出現， 但不於 POST/flash_price_campaigns出現。