Return offer id in Bolt12ReceiveResponse

Same motivation as the bolt11 change, allow us to track bolt 12 receives
without having to decode the offer.

Author: benthecarman

ldk-server-protos/src/api.rs

@@ -395,6 +395,9 @@ pub struct Bolt12ReceiveResponse {
 	/// to the recipient.
 	#[prost(string, tag = "1")]
 	pub offer: ::prost::alloc::string::String,
+	/// The hex-encoded offer id.
+	#[prost(string, tag = "2")]
+	pub offer_id: ::prost::alloc::string::String,
 }
 /// Send a payment for a BOLT12 offer.
 /// See more:

ldk-server-protos/src/proto/api.proto

@@ -328,6 +328,9 @@ message Bolt12ReceiveResponse {
   // With the details of the offer, the sender has all the data necessary to send a payment
   // to the recipient.
   string offer = 1;
+
+  // The hex-encoded offer id.
+  string offer_id = 2;
 }
 
 // Send a payment for a BOLT12 offer.

ldk-server/src/api/bolt12_receive.rs

@@ -7,6 +7,7 @@
 // You may not use this file except in accordance with one or both of these
 // licenses.
 
+use hex::DisplayHex;
 use ldk_server_protos::api::{Bolt12ReceiveRequest, Bolt12ReceiveResponse};
 
 use crate::api::error::LdkServerError;
@@ -28,6 +29,7 @@ pub(crate) fn handle_bolt12_receive_request(
 			.receive_variable_amount(&request.description, request.expiry_secs)?,
 	};
 
-	let response = Bolt12ReceiveResponse { offer: offer.to_string() };
+	let offer_id = offer.id().0.to_lower_hex_string();
+	let response = Bolt12ReceiveResponse { offer: offer.to_string(), offer_id };
 	Ok(response)
 }