add rake task to encrypt existing events data

lib/tasks/encrypt_event_columns.rake

@@ -0,0 +1,8 @@
+namespace :event do
+  desc "update events to be encrypted with ActiveRecord encryption"
+  task encrypt_sensitive_columns: :environment do
+    Event.all.find_each do |event|
+      event.encrypt
+    end
+  end
+end