Handle unread messages

[skitterm]

Description

As a user, I would like to be notified about unread messages when I open the app.

Tasks

• Determine how to UI-wise calculate "read"-ness of a message
• When user is on room, show message (but not room) notification
• When a message is read, remove notification from message and room
• When logging in, any unread messages show notification on message and room until read

Acceptance criteria

• When a user sends me a message and I am offline, the room and message show a notification when I log back into the app
• After viewing a message, the message and room notification disappear