Add Danbooru Winter Sale.

app/models/user.rb

@@ -404,7 +404,9 @@ class User < ApplicationRecord
     end
 
     def tag_query_limit
-      if is_platinum?
+      if is_member? && Danbooru.config.is_promotion?
+        1_000_000
+      elsif is_platinum?
         Danbooru.config.base_tag_query_limit * 2
       elsif is_gold?
         Danbooru.config.base_tag_query_limit

app/models/user_upgrade.rb

@@ -34,7 +34,11 @@ class UserUpgrade < ApplicationRecord
   end
 
   def self.gold_price
-    2000
+    if Danbooru.config.is_promotion?
+      1500
+    else
+      2000
+    end
   end
 
   def self.platinum_price