do not recalculate GroupOrder totals, but show message to do so on migrations

db/migrate/20130702113610_update_group_order_totals.rb

@@ -1,10 +1,16 @@
 class UpdateGroupOrderTotals < ActiveRecord::Migration
   def self.up
-    # The group_order total was updated to the total ordered amount instead of
-    # the amount received. Now this is fixed, the totals need to be updated.
-    GroupOrder.all.each do |go|
-      go.order.closed? and go.update_price!
-    end
+    say "If you have ever modified an order after it was settled, the group_order's " +
+        "price may be calculated incorrectly. This can take a lot of time on a " +
+        "large database."
+
+    say "If you do want to update the ordergroup totals, open the rails console " +
+        "(by running `rails c`), and enter:"
+
+    say "GroupOrder.all.each { |go| go.order.closed? and go.update_price! }", subitem: true
+
+    say "You may want to check first that no undesired accounting issues are introduced. " +
+        "It may be wise to discuss this with those responsible for the ordering finances."
   end
 
   def self.down