Add LSPS5 (bLIP-55) webhook notification support

Implement the bLIP-55 / LSPS5 webhook registration protocol on top of the
multi-LSP liquidity module (src/liquidity/{client,service}).

Client side, exposed via Node::liquidity().lsps5():
- set_webhook / list_webhooks / remove_webhook to manage webhook
  registrations with an LSP.
- When no node_id is given, set_webhook and remove_webhook fan out to every
  LSPS5-capable LSP so a webhook can be configured once across all configured
  LSPs; set_webhook returns one result per LSP that accepted the registration
  and remove_webhook returns the LSPs it was removed from.

Service side, enabled via Builder::enable_liquidity_provider_lsps5():
- Deliver outgoing webhook notifications over HTTP in response to
  LSPS5ServiceEvent::SendWebhookNotification.
- Automatically send an onion-message-incoming notification when an
  intercepted onion message targets a client that is currently offline
  (wired from LdkEvent::OnionMessageIntercepted, gated on peer connectivity).

Wires the feature through the UniFFI bindings and adds LSPS5-specific Error
variants.

Author: Camillarhi

bindings/ldk_node.udl

@@ -113,6 +113,7 @@ interface Node {
 	OnchainPayment onchain_payment();
 	UnifiedPayment unified_payment();
 	Liquidity liquidity();
+	LSPS5Liquidity lsps5_liquidity();
 	[Throws=NodeError]
 	void lnurl_auth(string lnurl);
 	[Throws=NodeError]
@@ -184,6 +185,8 @@ typedef interface UnifiedPayment;
 
 typedef interface Liquidity;
 
+typedef interface LSPS5Liquidity;
+
 [Error]
 enum NodeError {
 	"AlreadyRunning",
@@ -249,6 +252,9 @@ enum NodeError {
 	"InvalidLnurl",
 	"ChainSourceNotSupported",
 	"InvalidPayerProof",
+	"LiquiditySetWebhookFailed",
+	"LiquidityRemoveWebhookFailed",
+	"LiquidityListWebhooksFailed"
 };
 
 typedef dictionary NodeStatus;

src/builder.rs

@@ -83,8 +83,8 @@ use crate::runtime::{Runtime, RuntimeSpawner};
 use crate::tx_broadcaster::TransactionBroadcaster;
 use crate::types::{
 	AsyncPersister, ChainMonitor, ChannelManager, DynStore, DynStoreRef, DynStoreWrapper,
-	GossipSync, Graph, HRNResolver, KeysManager, MessageRouter, OnionMessenger, PaymentStore,
-	PeerManager, PendingPaymentStore,
+	GossipSync, Graph, HRNResolver, KeysManager, LSPS5ServiceConfig, MessageRouter, OnionMessenger,
+	PaymentStore, PeerManager, PendingPaymentStore,
 };
 use crate::wallet::persist::{read_address_pool, KVStoreWalletPersister};
 use crate::wallet::Wallet;
@@ -127,10 +127,12 @@ struct PathfindingScoresSyncConfig {
 
 #[derive(Debug, Clone, Default)]
 struct LiquiditySourceConfig {
-	// Acts for both LSPS1 and LSPS2 clients connecting to the given service.
+	// Acts for LSPS1, LSPS2 and LSPS5 clients connecting to the given service.
 	lsp_nodes: Vec<LspConfig>,
 	// Act as an LSPS2 service.
 	lsps2_service: Option<LSPS2ServiceConfig>,
+	// Act as an LSPS5 service.
+	lsps5_service: Option<LSPS5ServiceConfig>,
 }
 
 #[derive(Clone)]
@@ -522,6 +524,21 @@ impl NodeBuilder {
 		self
 	}
 
+	/// Configures the [`Node`] instance to provide an [bLIP-55 / LSPS5] service, enabling clients
+	/// to register webhooks for push notifications.
+	///
+	/// **Caution**: LSP service support is in **alpha** and is considered an experimental feature.
+	///
+	/// [bLIP-55 / LSPS5]: https://github.com/lightning/blips/blob/master/blip-0055.md
+	pub fn enable_liquidity_provider_lsps5(
+		&mut self, lsps5_service_config: LSPS5ServiceConfig,
+	) -> &mut Self {
+		let liquidity_source_config =
+			self.liquidity_source_config.get_or_insert(LiquiditySourceConfig::default());
+		liquidity_source_config.lsps5_service = Some(lsps5_service_config);
+		self
+	}
+
 	/// Sets the used storage directory path.
 	pub fn set_storage_dir_path(&mut self, storage_dir_path: String) -> &mut Self {
 		self.config.storage_dir_path = storage_dir_path;
@@ -1122,6 +1139,16 @@ impl ArcedNodeBuilder {
 		self.inner.write().expect("lock").enable_liquidity_provider(lsps2_service_config);
 	}
 
+	/// Configures the [`Node`] instance to provide an [bLIP-55 / LSPS5] service, enabling clients
+	/// to register webhooks for push notifications.
+	///
+	/// **Caution**: LSP service support is in **alpha** and is considered an experimental feature.
+	///
+	/// [bLIP-55 / LSPS5]: https://github.com/lightning/blips/blob/master/blip-0055.md
+	pub fn enable_liquidity_provider_lsps5(&self, lsps5_service_config: LSPS5ServiceConfig) {
+		self.inner.write().expect("lock").enable_liquidity_provider_lsps5(lsps5_service_config);
+	}
+
 	/// Sets the used storage directory path.
 	pub fn set_storage_dir_path(&self, storage_dir_path: String) {
 		self.inner.write().expect("lock").set_storage_dir_path(storage_dir_path);
@@ -2166,6 +2193,10 @@ fn build_with_store_internal(
 			lsc.lsps2_service.as_ref().map(|config| {
 				liquidity_source_builder.lsps2_service(promise_secret, config.clone())
 			});
+
+			lsc.lsps5_service
+				.as_ref()
+				.map(|config| liquidity_source_builder.lsps5_service(config.clone()));
 		}
 
 		let liquidity_source = runtime
@@ -2225,6 +2256,8 @@ fn build_with_store_internal(
 
 	liquidity_source.lsps2_service().set_peer_manager(Arc::downgrade(&peer_manager));
 
+	liquidity_source.lsps5_service().set_peer_manager(Arc::downgrade(&peer_manager));
+
 	let connection_manager = Arc::new(ConnectionManager::new(
 		Arc::clone(&peer_manager),
 		config.tor_config.clone(),

src/error.rs

@@ -143,6 +143,12 @@ pub enum Error {
 	ChainSourceNotSupported,
 	/// The provided payer proof is invalid.
 	InvalidPayerProof,
+	/// Failed to set a webhook with the LSP.
+	LiquiditySetWebhookFailed,
+	/// Failed to remove a webhook with the LSP.
+	LiquidityRemoveWebhookFailed,
+	/// Failed to list webhooks with the LSP.
+	LiquidityListWebhooksFailed,
 }
 
 impl fmt::Display for Error {
@@ -233,6 +239,15 @@ impl fmt::Display for Error {
 				write!(f, "The configured chain source is not supported.")
 			},
 			Self::InvalidPayerProof => write!(f, "The provided payer proof is invalid."),
+			Self::LiquiditySetWebhookFailed => {
+				write!(f, "Failed to set a webhook with the LSP.")
+			},
+			Self::LiquidityRemoveWebhookFailed => {
+				write!(f, "Failed to remove a webhook with the LSP.")
+			},
+			Self::LiquidityListWebhooksFailed => {
+				write!(f, "Failed to list webhooks with the LSP.")
+			},
 		}
 	}
 }

src/event.rs

@@ -2083,6 +2083,8 @@ where
 				} else {
 					log_error!(self.logger, "Onion message intercepted for unknown SCID");
 				}
+
+				self.liquidity_source.lsps5_service().notify_onion_message_incoming(peer_node_id);
 			},
 			LdkEvent::OnionMessagePeerConnected { peer_node_id } => {
 				if let Some(om_mailbox) = self.om_mailbox.as_ref() {