Joffrey JAFFEUX dbf3ff1738
FIX: correctly re-conciliate message bus backlog (#22020)
We have been struggling a lot on this lately as it's almost impossible to write a decent test for this.

The important things which need to happen:
- fetch the unread/mention state and last message bus channel ids of each chat channels
- stop all subscriptions
- restart global chat subscriptions
- update channels with new state and ensure the message bus ids are updated
- restart subscriptions of each chat channel

As a followup we need to start implementing a standard way to query for a resource state. Something similar to: `/channels/tracking` and `/channels/:id/tracking`

Each of these endpoints would return a state similar to:

```json
{
  tracking: { ... },
  message_bus_ids: { ... }
}
2023-06-09 09:00:24 +02:00
..
2023-05-16 19:40:01 +02:00
2023-05-31 09:15:16 +02:00