[#6574] Add a TimeEntryActivity to OverheadBudgets

db/migrate/021_add_time_entry_activity_id_to_overhead_budgets.rb

@@ -0,0 +1,10 @@
+class AddTimeEntryActivityIdToOverheadBudgets < ActiveRecord::Migration
+  def self.up
+    add_column :overhead_budgets, :time_entry_activity_id, :integer
+    add_index :overhead_budgets, :time_entry_activity_id
+  end
+
+  def self.down
+    remove_column :overhead_budgets, :time_entry_activity_id
+  end
+end