initial implementation of banning room IDs

takes a full room ID, evicts all our users from that room,
adds room ID to banned room IDs metadata db table, and
forbids any new local users from attempting to join it.

Signed-off-by: strawberry <strawberry@puppygock.gay>

src/service/rooms/metadata/data.rs

@@ -6,4 +6,7 @@ pub trait Data: Send + Sync {
     fn iter_ids<'a>(&'a self) -> Box<dyn Iterator<Item = Result<OwnedRoomId>> + 'a>;
     fn is_disabled(&self, room_id: &RoomId) -> Result<bool>;
     fn disable_room(&self, room_id: &RoomId, disabled: bool) -> Result<()>;
+    fn is_banned(&self, room_id: &RoomId) -> Result<bool>;
+    fn ban_room(&self, room_id: &RoomId, banned: bool) -> Result<()>;
+    fn list_banned_rooms<'a>(&'a self) -> Box<dyn Iterator<Item = Result<OwnedRoomId>> + 'a>;
 }