Add pathfinding scores export method

The exported scores can be shared with light nodes and used to improve
pathfinding when only a limited local view on the network is available.

bindings/ldk_node.udl

@@ -126,6 +126,8 @@ interface Node {
 	NetworkGraph network_graph();
 	string sign_message([ByRef]sequence<u8> msg);
 	boolean verify_signature([ByRef]sequence<u8> msg, [ByRef]string sig, [ByRef]PublicKey pkey);
+	[Throws=NodeError]
+	bytes export_pathfinding_scores();
 };
 
 [Enum]

src/lib.rs

@@ -99,8 +99,6 @@ mod wallet;
 pub use bip39;
 pub use bitcoin;
 pub use lightning;
-pub use lightning_invoice;
-pub use lightning_types;
 pub use vss_client;
 
 pub use balance::{BalanceDetails, LightningBalance, PendingSweepBalance};
@@ -1509,6 +1507,21 @@ impl Node {
 	pub fn verify_signature(&self, msg: &[u8], sig: &str, pkey: &PublicKey) -> bool {
 		self.keys_manager.verify_signature(msg, sig, pkey)
 	}
+
+	/// Exports the current state of the scorer. The result can be shared with and merged by light nodes that only have
+	/// a limited view of the network.
+	pub fn export_pathfinding_scores(&self) -> Result<Vec<u8>, Error> {
+		self.kv_store
+			.read(
+				lightning::util::persist::SCORER_PERSISTENCE_PRIMARY_NAMESPACE,
+				lightning::util::persist::SCORER_PERSISTENCE_SECONDARY_NAMESPACE,
+				lightning::util::persist::SCORER_PERSISTENCE_KEY,
+			)
+			.map_err(|e| {
+				log_error!(self.logger, "Failed to export pathfinding scores: {}", e);
+				Error::PersistenceFailed
+			})
+	}
 }
 
 impl Drop for Node {