Add task to migrate data to translation tables

We forgot to do it when we created the translation tables, and so now we
need to make sure we don't overwrite existing translations.

spec/lib/tasks/globalize_spec.rb

@@ -0,0 +1,76 @@
+require "rails_helper"
+require "rake"
+
+describe "Globalize tasks" do
+
+  describe "#migrate_data" do
+
+    before do
+      Rake.application.rake_require "tasks/globalize"
+      Rake::Task.define_task(:environment)
+    end
+
+    let :run_rake_task do
+      Rake::Task["globalize:migrate_data"].reenable
+      Rake.application.invoke_task "globalize:migrate_data"
+    end
+
+    context "Original data with no translated data" do
+      let(:poll) do
+        create(:poll).tap do |poll|
+          poll.translations.delete_all
+          poll.update_column(:name, "Original")
+          poll.reload
+        end
+      end
+
+      it "copies the original data" do
+        expect(poll.send(:"name_#{I18n.locale}")).to be nil
+        expect(poll.name).to eq("Original")
+
+        run_rake_task
+        poll.reload
+
+        expect(poll.name).to eq("Original")
+        expect(poll.send(:"name_#{I18n.locale}")).to eq("Original")
+      end
+    end
+
+    context "Original data with blank translated data" do
+      let(:banner) do
+        create(:banner).tap do |banner|
+          banner.update_column(:title, "Original")
+          banner.translations.first.update_column(:title, "")
+        end
+      end
+
+      it "copies the original data" do
+        expect(banner.title).to eq("")
+
+        run_rake_task
+        banner.reload
+
+        expect(banner.title).to eq("Original")
+        expect(banner.send(:"title_#{I18n.locale}")).to eq("Original")
+      end
+    end
+
+    context "Original data with translated data" do
+      let(:notification) do
+        create(:admin_notification, title: "Translated").tap do |notification|
+          notification.update_column(:title, "Original")
+        end
+      end
+
+      it "maintains the translated data" do
+        expect(notification.title).to eq("Translated")
+
+        run_rake_task
+        notification.reload
+
+        expect(notification.title).to eq("Translated")
+        expect(notification.send(:"title_#{I18n.locale}")).to eq("Translated")
+      end
+    end
+  end
+end