DISABLE_SESSION define is changed so that existing session are continued
but new sessions are not saved. This allows external auth backends to
redirect to an external site and that site redirect back to a `/api` URL and
the user's session will be continued.

Reviewed-By: Peter Rotich <peter@osticket.com>

It is possible that a recipient received and processed by the system may not
have a name set. In that case, the email mailbox should be used. As a
failsafe, avoid crashing if the User::save() should fail.

oops: Fixup registration for existing users

Reviewed-By: Peter Rotich <peter@osticket.com>

This occurs for attachments added via the staff or client web interfaces

Upgrade to Redactor 9.2.1

PJAX for the staff control panel