service= redirect URL is not checked when logging out from CAS, to avoid
insecure redirect attacks. The verification is only made if CAS access
control is enabled.
In order for this to work in common cases (applications redirects to an
unprotected page after logout), we add CAS App domains to the list of
globally trusted domains.
If your application wants to redirect to a third-party domain, it needs
to be added to LLNG's trustedDomains
