add an attribute 'root_id' to source_channel_metadata object when it doesn't exist
add an attribute 'root_id' to source_channel_metadata object when it doesn't exist

lyw07/kolibri,indirectlylit/kolibri,indirectlylit/kolibri,jonboiser/kolibri,benjaoming/kolibri,mrpau/kolibri,mrpau/kolibri,learningequality/kolibri,benjaoming/kolibri,learningequality/kolibri,DXCanas/kolibri,jonboiser/kolibri,indirectlylit/kolibri,lyw07/kolibri,jonboiser/kolibri,indirectlylit/kolibri,lyw07/kolibri,DXCanas/kolibri,DXCanas/kolibri,DXCanas/kolibri,mrpau/kolibri,lyw07/kolibri,jonboiser/kolibri,benjaoming/kolibri,learningequality/kolibri,mrpau/kolibri,benjaoming/kolibri,learningequality/kolibri