graph/db: introduce VersionedGraph

For now, all instances will use V1 only so as not to change behaviour
yet.

rpcserver.go

@@ -746,7 +746,7 @@ func (r *rpcServer) addDeps(ctx context.Context, s *server,
 			return info.NodeKey1Bytes, info.NodeKey2Bytes, nil
 		},
 		HasNode: func(nodePub route.Vertex) (bool, error) {
-			exists, err := graph.HasNode(ctx, nodePub)
+			exists, err := s.v1Graph.HasNode(ctx, nodePub)
 
 			return exists, err
 		},
@@ -1821,7 +1821,7 @@ func (r *rpcServer) VerifyMessage(ctx context.Context,
 	// channels signed the message.
 	//
 	// TODO(phlip9): Require valid nodes to have capital in active channels.
-	graph := r.server.graphDB
+	graph := r.server.v1Graph
 	active, err := graph.HasNode(ctx, pub)
 	if err != nil {
 		return nil, fmt.Errorf("failed to query graph: %w", err)
@@ -7143,7 +7143,7 @@ func (r *rpcServer) GetNodeInfo(ctx context.Context,
 			"include_channels")
 	}
 
-	graph := r.server.graphDB
+	graph := r.server.v1Graph
 
 	// First, parse the hex-encoded public key into a full in-memory public
 	// key object we can work with for querying.
@@ -8298,7 +8298,7 @@ func (r *rpcServer) ForwardingHistory(ctx context.Context,
 			return "", err
 		}
 
-		peer, err := r.server.graphDB.FetchNode(ctx, vertex)
+		peer, err := r.server.v1Graph.FetchNode(ctx, vertex)
 		if err != nil {
 			return "", err
 		}