New notifications for timeline/milestones

[vikasrohit]

@vic-topcoder @acshields this is an extension to #2178. Can you please come up with all possible events related to milestones which we should convert into notifications?

fyi @gondzo

Aha! Link: https://topcoder.aha.io/features/TCCONNECT-390

[vic-georgiev]

Should be added to https://docs.google.com/spreadsheets/d/15u4cwCg5BwgyJkVsd-wp_T2pUnDrqW2bEZuwAn3qArA/edit?usp=sharing

[vikasrohit]

Done, right now customers won't see any of the timeline/milestone specific notifications except when a milestone is waiting for customer input. Only managers/copilot would see milestone activated/completed notifications.