Filter trade lists to active users only

I don't have the cute fancy UI with trade list names included, but! Now
the trade ratios should match DTI 2020 and that's nice!

app/controllers/items_controller.rb

@@ -72,7 +72,7 @@ class ItemsController < ApplicationController
           includes_child_translations.group_by(&:species)
 
         trading_closet_hangers = @item.closet_hangers.trading.newest.
-          includes(:user)
+          user_is_active.includes(:user)
 
         @trading_closet_hangers_by_owned = {
           true => trading_closet_hangers.filter { |c| c.owned? },

app/models/closet_hanger.rb

@@ -46,6 +46,10 @@ class ClosetHanger < ApplicationRecord
   scope :newest, -> { order(arel_table[:created_at].desc) }
   scope :owned_before_wanted, -> { order(arel_table[:owned].desc) }
   scope :unlisted, -> { where(:list_id => nil) }
+  scope :user_is_active, -> {
+    u = User.arel_table
+    joins(:user).where(u[:last_trade_activity_at].gteq(6.months.ago))
+  }
 
   before_validation :merge_quantities, :set_owned_by_list