Implement room v12 (#943)

**Does not yet work!** Currently, state resolution does not correctly resolve conflicting states. Everything else appears to work as expected, so stateres will be fixed soon, then we should be clear for takeoff.

Also: a lot of things currently accept a nullable room ID that really just don't need to. This will need tidying up before merge. Some authentication checks have also been disabled temporarily but nothing important.

A lot of things are tagged with `TODO(hydra)`, those need resolving before merge. External contributors should PR to the `hydra/public` branch, *not* ` main`.

---

This PR should be squash merged.

Reviewed-on: https://forgejo.ellis.link/continuwuation/continuwuity/pulls/943
Co-authored-by: nexy7574 <git@nexy7574.co.uk>
Co-committed-by: nexy7574 <git@nexy7574.co.uk>

src/api/server/backfill.rs

@@ -2,7 +2,7 @@ use std::cmp;
 
 use axum::extract::State;
 use conduwuit::{
-	PduCount, Result,
+	Event, PduCount, Result,
 	utils::{IterStream, ReadyExt, stream::TryTools},
 };
 use futures::{FutureExt, StreamExt, TryStreamExt};
@@ -68,7 +68,7 @@ pub(crate) async fn get_backfill_route(
 				Ok(services
 					.rooms
 					.state_accessor
-					.server_can_see_event(body.origin(), &pdu.room_id, &pdu.event_id)
+					.server_can_see_event(body.origin(), &pdu.room_id_or_hash(), &pdu.event_id)
 					.await
 					.then_some(pdu))
 			})