unique_together integration in CW (alf+syt) * added in-DB representation of the constraint with a new entity type (CWUniqueTogetherConstraint) * the schema is now migrated on a sync_schema_props_perms(EType) call in the migration script * removed the migration commands provided in the first implementation

if not rql('CWConstraintType X WHERE X name "RQLUniqueConstraint"',
           ask_confirm=False):
    rql('INSERT CWConstraintType X: X name "RQLUniqueConstraint"',
        ask_confirm=False)