@Override
    public String getIdentifier() {
        return PROVIDER_IDENTIFER;
    }
Creates a new DuoAuthenticationProvider that verifies users
using the Duo authentication service

@throws GuacamoleException
    If a required property is missing, or an error occurs while parsing
    a property.
extensions/guacamole-auth-duo/src/main/java/org/apache/guacamole/auth/duo/DuoAuthenticationProvider.java