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/client/membership/mod.rs

@@ -69,11 +69,11 @@ pub(crate) async fn banned_room_check(
 	}
 
 	if let Some(room_id) = room_id {
-		if services.rooms.metadata.is_banned(room_id).await
-			|| services
-				.moderation
-				.is_remote_server_forbidden(room_id.server_name().expect("legacy room mxid"))
-		{
+		let room_banned = services.rooms.metadata.is_banned(room_id).await;
+		let server_banned = room_id.server_name().is_some_and(|server_name| {
+			services.moderation.is_remote_server_forbidden(server_name)
+		});
+		if room_banned || server_banned {
 			warn!(
 				"User {user_id} who is not an admin attempted to send an invite for or \
 				 attempted to join a banned room or banned room server name: {room_id}"
@@ -106,7 +106,6 @@ pub(crate) async fn banned_room_check(
 					.boxed()
 					.await?;
 			}
-
 			return Err!(Request(Forbidden("This room is banned on this homeserver.")));
 		}
 	} else if let Some(server_name) = server_name {