I think it's understood that for this pull request we're not going to do the stateful stuff, much of which is dependent on the ability to revoke/modify notifications.  But let's put a big TODO/FUTURE WORK comment in here to that effect.  Like:

```
// TODO: Persist the set of currently reported-as-new messages so that if
// we have X new messages that are previously reported, and we get Y more
// new ones, our notification state is the same if we got X then Y, or if we got
// X+Y in one go.
```