Users disconnecting and going offline

[keithamoss]

Users can opt to stop receiving assignments (going inactive), but we're going to need to handle users going offline and disconnecting. This can happen by:

• Their own choice (e.g. closes browser tab)
• At the application level (e.g. we deploy a new build and a new server comes up)
• Further upstream (e.g. their internet goes down)

We don't want to spam folks with "User is offline/online" notices, so have a think about how to approach this. Off the top of my head:

• When the user connects to the web socket server update a timestamp on their profile
• When the user disconnects/closes the web socket connection log a celery task with a delayed start that will set the user as offline and send a notice if it wakes up and finds that the user hasn't reconnected since the disconnection/offline that triggered the task

Discussion from user testing:

• Being disconnected (in a networking sense) = always show as offline
• On reconnecting / reloading, if offline show prompt. (Only on the queue view or everywhere?)
• Give them 30s grace to allow them to reconnect (e.g. if they close the tab by mistake)
• When reconnecting we'll need to ensure all appropriate state is resynced. I think we're good for everything except the new column state for triage? Think about this to double check :)