Feature Request: Messaging for users and/or communities

Requesting the introduction of a messaging system that would allow users to message other users in the same community, allow authorized users to message an entire community, and allow administrators to broadcast messages to all logged-in users.

Business requirement:

[li]Business user needs to collaborate in real-time with another business user on a content item[/li][li]Business manager needs to send a community message about urgent changes that impact the entire community[/li][li]Administrators need to restart the application for maintenance[/li][/ol]