New bus events for milestone notifications

[vikasrohit]

Need to support few new events for milestones similar to what we did for project plan earlier in #110.

Current list of events is:

notifications.connect.project.phase.milestone.transition.active => when milestone is marked as active
notifications.connect.project.phase.milestone.transition.completed => when milestone is marked as complete
notifications.connect.project.phase.milestone.waiting.customer => when milestones are waiting for customers's input (this might be tricky to identify because every milestone type has different way to identify that it is waiting for customer input and that is stored in details json)

[ngoctay]

@vikasrohit @gondzo
I will make a commit for the first 2 events.
For the last one (waiting.customer), will leave a TODO in the code so that we can tackle it later when we have more details.

[vikasrohit]

@ngoctay can you please raise the ...waiting.customer event when we find details.metadata.waitingForCustomer flag to exist and equal to true? As of now, we don't have a unique way to identify that a milestone is waiting for customer input, so we are thinking of keeping a new flag at mentioned level to capture this details. This field would be updated by front end. Ideally, we don't want to parse the details field in backend but I think we are good in this case as it would be a standard flag across milestones and we would keep details.content as milestone specific data which we would never parse on backend.

[vikasrohit]

It was not working for active event when the milestone is made active as cascaded effect after marking previous milestone as completed and this was happening because we were using cascadedUpdates instead of cascadedUpdates.milestones to iterate over milestones updated via cascade. After fixing that it is working fine now for active and completed events, however, we need to do some changes in front end to validate the waiting.customer event.
Marking the issue closed. Will take care of waiting.customer event separately after front end changes.
@gondzo please feel free to tag it as per convenience for payments.