tests: update bolt12_proof_of_payment test for enum pattern

This patch updates the bolt12_proof_of_payment test to use pattern
matching on the new PaidBolt12Invoice enum instead of checking the
kind field and accessing optional invoice fields.

Problem:
The test was using the old struct-based API with .kind field and
.bolt12_invoice.as_ref(), which no longer exists after converting
PaidBolt12Invoice to an enum.

Solution:
Use Rust pattern matching on the PaidBolt12Invoice enum to extract
the invoice directly from the variant, which is more idiomatic and
takes advantage of the type system.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: vincenzopalazzo

tests/integration_tests_rust.rs

@@ -30,7 +30,7 @@ use ldk_node::config::{AsyncPaymentsRole, EsploraSyncConfig};
 use ldk_node::entropy::NodeEntropy;
 use ldk_node::liquidity::LSPS2ServiceConfig;
 use ldk_node::payment::{
-	ConfirmationStatus, PaidBolt12InvoiceKind, PaymentDetails, PaymentDirection, PaymentKind,
+	ConfirmationStatus, PaidBolt12Invoice, PaymentDetails, PaymentDirection, PaymentKind,
 	PaymentStatus, UnifiedPaymentResult,
 };
 use ldk_node::{Builder, Event, NodeError};
@@ -1367,11 +1367,15 @@ async fn bolt12_proof_of_payment() {
 			// Verify the BOLT12 invoice is present and contains the correct payment hash
 			let paid_invoice =
 				bolt12_invoice.expect("bolt12_invoice should be present for BOLT12 payments");
-			assert_eq!(paid_invoice.kind, PaidBolt12InvoiceKind::Bolt12Invoice);
-			let invoice =
-				paid_invoice.bolt12_invoice.as_ref().expect("bolt12_invoice should be present");
-			assert_eq!(invoice.payment_hash(), payment_hash);
-			assert_eq!(invoice.amount_msats(), expected_amount_msat);
+			match paid_invoice {
+				PaidBolt12Invoice::Bolt12Invoice(invoice) => {
+					assert_eq!(invoice.payment_hash(), payment_hash);
+					assert_eq!(invoice.amount_msats(), expected_amount_msat);
+				},
+				PaidBolt12Invoice::StaticInvoice(_) => {
+					panic!("Expected Bolt12Invoice, got StaticInvoice");
+				},
+			}
 
 			node_a.event_handled().unwrap();
 		},