Another massive refactor to change the way routing works. Now any
column can route anywhere.
Also things are generally just much better and more modular via the
new struct split borrowing technique.
I didn't even try to split this into smaller commits for my sanity.
Signed-off-by: William Casarin <jb55@jb55.com>
This adds local nostrdb thread subscriptions. When navigating to a
thread, we first check to see if we have any active nostrdb
subscriptions for that thread. If not, we create a new subscription. If
we do, we re-use that subscription.
This works by storing thread state in the Threads struct in the Damus
application state.
When we pop a route, we check to see if its a thread route. If it is,
then we try to unsubscribe, but only if that is the last remaining
subscriber for that thread, as there could be more than one.
Signed-off-by: William Casarin <jb55@jb55.com>