feat: Convert Bolt11Invoice from string type to full interface in UDL

- Replace [Custom] typedef string Bolt11Invoice with interface definition
- Define required Bolt11Invoice methods in the UDL interface (expiry_time, min_final_cltv_expiry_delta, amount_milli_satoshis, is_expired, etc.)

Author: alexanderwiederin

bindings/ldk_node.udl

@@ -693,6 +693,18 @@ dictionary NodeAnnouncementInfo {
 	sequence<SocketAddress> addresses;
 };
 
+interface Bolt11Invoice {
+	sequence<u8> signable_hash();
+	u64 expiry_time();
+	u64 min_final_cltv_expiry_delta();
+	u64? amount_milli_satoshis();
+	boolean is_expired();
+	u64 duration_since_epoch();
+	boolean would_expire(u64 at_time);
+	u64 duration_until_expiry();
+	PaymentHash payment_hash();
+};
+
 [Custom]
 typedef string Txid;
 
@@ -711,9 +723,6 @@ typedef string NodeId;
 [Custom]
 typedef string Address;
 
-[Custom]
-typedef string Bolt11Invoice;
-
 [Custom]
 typedef string Offer;