@Override
        public String getName() { return "duo-api-hostname"; }
The property within guacamole.properties which defines the hostname
of the Duo API endpoint to be used to verify user identities. This will
usually be in the form "api-XXXXXXXX.duosecurity.com", where "XXXXXXXX"
is some arbitrary alphanumeric value assigned by Duo and specific to
your organization.
extensions/guacamole-auth-duo/src/main/java/org/apache/guacamole/auth/duo/conf/ConfigurationService.java