[imp] Horde_SessionObjects

[liam hoekenga]

We're trying to figure out how to better tune our DB since the inclusion of
Horde_SessionObjects in the session data occasionally makes our sessions
unmanagably large (causing mysql to crash - we're using the mysql shared
session handler).

I need to know how reliably get something to show up as a session object in the
session data.  I've tried composing and reading messages w/ attachments (both
as "inline" and "attachment").  Neither seems to do it.  What situations create
session object entries?

Liam