Regardless of the configuration of the help desk registration, allow users
to receive ticket links via email. This patch enables the display and
operation of the ticket access link unless a user login is requested by the
user or specifically required by the system.

Instead of always showing the tickets page

If a client is already logged into the system and follows a second ticket
link, show the ticket instead of the list of tickets.

SSO was originally used for a SSO plugin. The backend has since been
refactored to support other authentication backends.