add comprehensive integration tests for webhook protocols

- Add integration tests for LSPS5 covering:
  - Webhook registration flow with request ID matching.
  - Error handling for invalid URLs, app names, and protocol mismatches.
  - Notification delivery for different event types (payment_incoming, expiry_soon, liquidity_management_request).
  - Idempotency of webhook registrations and update detection.
  - Replay prevention, tampering, and out-of-window timestamp validations.
- Extend LSPS2 integration tests to verify protocol message handling.

Author: martinsaposnic

lightning-liquidity/tests/lsps2_integration_tests.rs

@@ -88,13 +88,15 @@ fn invoice_generation_flow() {
 		#[cfg(lsps1_service)]
 		lsps1_service_config: None,
 		lsps2_service_config: Some(lsps2_service_config),
+		lsps5_service_config: None,
 		advertise_service: true,
 	};
 
 	let lsps2_client_config = LSPS2ClientConfig::default();
 	let client_config = LiquidityClientConfig {
 		lsps1_client_config: None,
 		lsps2_client_config: Some(lsps2_client_config),
+		lsps5_client_config: None,
 	};
 
 	let (service_node, client_node) =