id	summary	reporter	owner	description	type	status	priority	milestone	component	resolution	keywords	cc	repo	theme
1136	Move to SessionExtension in vdm	rgrp	kindly	When vdm was created there was no !SessionExtension so we use !MapperExtension for doing revisioning. Now that SessionExtension exists we should use it. We can also follow the existing SQLAlchemy recipe: <http://www.sqlalchemy.org/docs/orm/examples.html?highlight=versioning#versioned-objects>	enhancement	assigned	critical		vdm				vdm	none