add balance promotion shop promotion

app/models/balance_promotion.rb

@@ -1,7 +1,8 @@
 class BalancePromotion < ActiveRecord::Base
     has_paper_trail
     self.table_name = "balance_promotions"
-    has_and_belongs_to_many :depart_record
+    has_and_belongs_to_many :depart_record, :join_table => :depart_records_balance_promotions
+
 
     validates :begin_time,:end_time,:name,:min_total,:max_total, presence: true
     validate :product_validation