As outlined in https://github.com/matrix-org/gomatrixserverlib/pull/368
The main change Dendrite side is that `RoomVersion` no longer has any
methods on it. Instead, you need to bounce via `gmsl.GetRoomVersion`.
It's very interesting to see where exactly Dendrite cares about this.
For some places it's creating events (fine) but others are way more
specific. Those areas will need to migrate to GMSL at some point.
This adds store & forward relays into dendrite for p2p.
A few things have changed:
- new relay api serves new http endpoints for s&f federation
- updated outbound federation queueing which will attempt to forward
using s&f if appropriate
- database entries to track s&f relays for other nodes
