* The same as {@link SecurityContextImpl} but doesn't serialize {@link Authentication}.
*
* <p>
* {@link Authentication} often contains {@link UserDetails} implemented by a plugin,
* but when it's persisted as a part of {@link HttpSession}, such instance will never
* de-serialize correctly because the container isn't aware of additional classloading
* in Hudson.
*
* <p>
* Jenkins doesn't work with a clustering anyway, and so it's better to just not persist
* Authentication at all.
*
* See <a href="http://jenkins.361315.n4.nabble.com/ActiveDirectory-Plugin-ClassNotFoundException-while-loading-persisted-sessions-tp376451.html">the problem report</a>.