OctaviusSessionHolder
Holds the session bound to the current transaction: by OctaviusJdbcTransactionManager for a transaction it begins, and by OctaviusTemplate for one another manager began, or for synchronization with no transaction behind it.
A session lasts as long as the transaction does rather than as long as one OctaviusTemplate.execute call: opening one per call would build a notification, copy and type manager each time, and would leave the question of which of them undoes the state on the connection unanswered.