Create a per-client session with the router. The user is
authenticated through the SSL certificates that have been
associated with the connection. If a
SessionManager has been
installed, a proxy to a
Session object is returned to the
client. Otherwise, null is returned and only an internal
session (i.e., not visible to the client) is created.
If a session proxy is returned, it must be configured to route
through the router that created it. This will happen automatically
if the router is configured as the client's default router at the
time the session proxy is created in the client process, otherwise
the client must configure the session proxy explicitly.