You can use a a redirecting service to create a friendly URL for your end-users to use instead of the long EAS SAML URL. Redirecting services like https://redirection.io/ and https://www.easyredir.com/ are common options. Or you can search for similar redirecting services.
One thing to note is that a DNS cannot handle directing to paths (URL is https://auth.agilquest.com/eas-saml/saml/web/auth/SAMPLE, the path is /eas-saml/saml/web/auth/SAMPLE), but a redirecting service can.
We cannot use an IP because each Reserve component sits behind at least one load balancer, and the load balancers determine where the traffic goes by the header information (the https:/auth.agilquest.com). Also, as of right now, Reserve determines what it's going to do based on the path. A redirect service is the way to accomplish a friendly URL.