public String getAPIHostname() throws GuacamoleException {
        return environment.getRequiredProperty(DUO_API_HOSTNAME);
    }
Returns the hostname of the Duo API endpoint to be used to verify user
identities, as defined in guacamole.properties by the "duo-api-hostname"
property. 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.

@return
    The hostname of the Duo API endpoint to be used to verify user
    identities.

@throws GuacamoleException
    If the associated property within guacamole.properties is missing.
extensions/guacamole-auth-duo/src/main/java/org/apache/guacamole/auth/duo/conf/ConfigurationService.java