jobs: migrate related tag updates to ActiveJob.

test/unit/tag_test.rb

@@ -283,4 +283,15 @@ class TagTest < ActiveSupport::TestCase
       assert_equal(1, tag.reload.post_count)
     end
   end
+
+  context "The #related_tag_array method" do
+    should "update the related tags" do
+      create(:post, tag_string: "bkub")
+      tag = Tag.find_by_name("bkub")
+
+      assert_nil(tag.related_tags)
+      perform_enqueued_jobs { tag.related_tag_array }
+      assert_equal([["bkub", "1"]], tag.reload.related_tag_array)
+    end
+  end
 end