Update verbiage from to "Authentication"

Author: crweiner

use_cases/domain_authentication.md

@@ -0,0 +1,5 @@
+# How to Setup a Domain Authentication
+
+You can find documentation for how to setup Sender Authentication via the UI [here](https://sendgrid.com/docs/ui/account-and-settings/how-to-set-up-domain-authentication/) and via API [here](https://github.com/sendgrid/sendgrid-python/blob/master/USAGE.md#sender-authentication).
+
+Find more information about all of SendGrid's Authenticating related documentation [here](https://sendgrid.com/docs/ui/account-and-settings/how-to-set-up-domain-authentication/).