Show description of chat at beginning of history

[gnunicorn]

When joining a fresh chat, at the beginning of history we want to show the chat description prominently in the timeline.

• [ ] Ideally the admin can also quickly edit it from right there
• [ ] and invite new users.

Additionally we want to

• [ ] track whether a user already entered a chat room
• [ ] and if they haven't yet and there is a description, we want to prominently show the description once