public void Test_EnablingGoogleAnalytics()
        {
            var mail = BasicMailBuilder
                       .EnableGoogleAnalytics("source", "medium", "term", content: "content", campaign: "campaign")
                       .Build();

            var message = new SendGridMessage();

            message.EnableGoogleAnalytics("source", "medium", "term", content: "content", campaign: "campaign");
            Assert.IsFalse(string.IsNullOrEmpty(message.Header.JsonString()));
            Assert.AreEqual(message.Header.JsonString(), mail.Header.JsonString());
        }