Update create_refund_builder to exclusively use create_blinded_paths

Reasoning:

The reasoning remains the same as for the `create_offer_builder` case,
ensuring consistency in the default behavior and maintaining flexibility
for custom implementations.

Author: shaavan

lightning/src/ln/offers_tests.rs

@@ -455,8 +455,9 @@ fn creates_short_lived_refund() {
 
 	let absolute_expiry = bob.offers_handler.duration_since_epoch() + MAX_SHORT_LIVED_RELATIVE_EXPIRY;
 	let payment_id = PaymentId([1; 32]);
+	let router = DefaultMessageRouter::compact_blinded_paths(bob.network_graph, bob.node.entropy_source);
 	let refund = bob.offers_handler
-		.create_refund_builder(10_000_000, absolute_expiry, payment_id, Retry::Attempts(0), None)
+		.create_refund_builder_using_router(router, 10_000_000, absolute_expiry, payment_id, Retry::Attempts(0), None)
 		.unwrap()
 		.build().unwrap();
 	assert_eq!(refund.absolute_expiry(), Some(absolute_expiry));

lightning/src/offers/flow.rs

@@ -1331,17 +1331,19 @@ macro_rules! create_refund_builder { ($self: ident, $builder: ty) => {
 		let secp_ctx = &$self.secp_ctx;
 
 		let nonce = Nonce::from_entropy_source(entropy);
-		let context = OffersContext::OutboundPayment { payment_id, nonce, hmac: None };
-		let path = $self.create_blinded_paths_using_absolute_expiry(context, Some(absolute_expiry))
-			.and_then(|paths| paths.into_iter().next().ok_or(()))
+		let context = MessageContext::Offers(OffersContext::OutboundPayment { payment_id, nonce, hmac: None });
+		let paths = $self.create_blinded_paths(context)
 			.map_err(|_| Bolt12SemanticError::MissingPaths)?;
 
-		let builder = RefundBuilder::deriving_signing_pubkey(
+		let mut builder = RefundBuilder::deriving_signing_pubkey(
 			node_id, expanded_key, nonce, secp_ctx, amount_msats, payment_id
 		)?
 			.chain_hash($self.commons.get_chain_hash())
-			.absolute_expiry(absolute_expiry)
-			.path(path);
+			.absolute_expiry(absolute_expiry);
+
+		for path in paths {
+			builder = builder.path(path);
+		}
 
 		let expiration = StaleExpiration::AbsoluteTimeout(absolute_expiry);