public interface PromotionService {

  @GET("/promotions")
  Observable<Response<List<Promotion>>> fetchPromotions();

  @GET("/promotions/{promotion_id}/sales")
  Observable<Response<List<Sale>>> fetchSales(@Path("promotion_id") long promotionId);

  @GET("/promotions/{promotion_id}/ads")
  Observable<Response<List<Ad>>> fetchAds(@Path("promotion_id") long promotionId);

}