Add handle_held_htlc_available MessageContext param

Needed to authenticate that the held_htlc_available message is being sent over
a reply path that we originally created and that isn't expired before we reply
with release_held_htlc. This context will be used in upcoming commits when we
add support for async receive.

fuzz/src/onion_message.rs

@@ -122,7 +122,8 @@ struct TestAsyncPaymentsMessageHandler {}
 
 impl AsyncPaymentsMessageHandler for TestAsyncPaymentsMessageHandler {
 	fn handle_held_htlc_available(
-		&self, _message: HeldHtlcAvailable, responder: Option<Responder>,
+		&self, _message: HeldHtlcAvailable, _context: AsyncPaymentsContext,
+		responder: Option<Responder>,
 	) -> Option<(ReleaseHeldHtlc, ResponseInstruction)> {
 		let responder = match responder {
 			Some(resp) => resp,

lightning/src/ln/channelmanager.rs

@@ -12166,7 +12166,8 @@ where
 	L::Target: Logger,
 {
 	fn handle_held_htlc_available(
-		&self, _message: HeldHtlcAvailable, _responder: Option<Responder>
+		&self, _message: HeldHtlcAvailable, _context: AsyncPaymentsContext,
+		_responder: Option<Responder>
 	) -> Option<(ReleaseHeldHtlc, ResponseInstruction)> {
 		None
 	}

lightning/src/ln/peer_handler.rs

@@ -149,7 +149,8 @@ impl OffersMessageHandler for IgnoringMessageHandler {
 }
 impl AsyncPaymentsMessageHandler for IgnoringMessageHandler {
 	fn handle_held_htlc_available(
-		&self, _message: HeldHtlcAvailable, _responder: Option<Responder>,
+		&self, _message: HeldHtlcAvailable, _context: AsyncPaymentsContext,
+		_responder: Option<Responder>,
 	) -> Option<(ReleaseHeldHtlc, ResponseInstruction)> {
 		None
 	}

lightning/src/onion_message/async_payments.rs

@@ -28,7 +28,8 @@ pub trait AsyncPaymentsMessageHandler {
 	/// Handle a [`HeldHtlcAvailable`] message. A [`ReleaseHeldHtlc`] should be returned to release
 	/// the held funds.
 	fn handle_held_htlc_available(
-		&self, message: HeldHtlcAvailable, responder: Option<Responder>,
+		&self, message: HeldHtlcAvailable, context: AsyncPaymentsContext,
+		responder: Option<Responder>,
 	) -> Option<(ReleaseHeldHtlc, ResponseInstruction)>;
 
 	/// Handle a [`ReleaseHeldHtlc`] message. If authentication of the message succeeds, an HTLC

lightning/src/onion_message/functional_tests.rs

@@ -85,7 +85,8 @@ struct TestAsyncPaymentsMessageHandler {}
 
 impl AsyncPaymentsMessageHandler for TestAsyncPaymentsMessageHandler {
 	fn handle_held_htlc_available(
-		&self, _message: HeldHtlcAvailable, _responder: Option<Responder>,
+		&self, _message: HeldHtlcAvailable, _context: AsyncPaymentsContext,
+		_responder: Option<Responder>,
 	) -> Option<(ReleaseHeldHtlc, ResponseInstruction)> {
 		None
 	}

lightning/src/onion_message/messenger.rs

@@ -1646,8 +1646,16 @@ where
 					},
 					#[cfg(async_payments)]
 					ParsedOnionMessageContents::AsyncPayments(AsyncPaymentsMessage::HeldHtlcAvailable(msg)) => {
+						let context = match context {
+							Some(MessageContext::AsyncPayments(context)) => context,
+							Some(_) => {
+								debug_assert!(false, "Checked in peel_onion_message");
+								return
+							},
+							None => return,
+						};
 						let response_instructions = self.async_payments_handler.handle_held_htlc_available(
-							msg, responder
+							msg, context, responder
 						);
 						if let Some((msg, instructions)) = response_instructions {
 							let _ = self.handle_onion_message_response(msg, instructions);