206c19e99e
Notifications are an unusual case in that we need users to manually opt in to new incompatible message formats by editing configuration because there may be external consumers expecting the old format. Add a send_notification() method to the driver interface and add a format version paramater to the method, to make it clear that this version selection is specifically for notifications. In the case of the rabbit/qpid drivers, the 2.0 format is where we added the message envelope. Change-Id: Ib4925c308b1252503749962aa16f043281f2b429