As an ONAP SDC pub-sub user I would like the following promise logic supported for specific actions:

1. The plug-in will initialize itself with a list of event names that SDC should receive completion notification - eventsToWait. This list is an optional parameter.
2. The SDC hub will store eventsToWait list for each registered plug-in and use it as follows:
   1. The notify implementation should return observable (only for actions in the stored list) and only when its state is “Action Completed” the flow will proceed as required.
   2. The observable will be resolved immediately when current event is not in the “eventsToWait” list.

DOD:

1. SDC will wait only for the actions defined on the eventsToWait list before proceeding with SDC flow.
2. Update design document with the new flows.