Add a counterparty_node_id to ClaimedHTLC in claimed events

When we claim a payment, `Event::PaymentClaimed` contains a list of
the HTLCs we claimed from as `ClaimedHTLC` objects. While they
include a `channel_id` the pyment came to us over, in theory
`channel_id`s aren't guaranteed to be unique (though in practice
they are in all opened channels aside from 0conf ones with a
malicious counterparty). Further, our APIs often require passing
both the `counterparty_node_id` and the `channel_id` to do things
to chanels.

Thus, here we add the missing `counterparty_node-id` to
`ClaimedHTLC`.

Author: TheBlueMatt

lightning/src/events/mod.rs

@@ -233,6 +233,11 @@ impl_writeable_tlv_based_enum_legacy!(PaymentPurpose,
 /// Information about an HTLC that is part of a payment that can be claimed.
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub struct ClaimedHTLC {
+	/// The counterparty of the channel.
+	///
+	/// This value will always be `None` for objects serialized with LDK versions prior to 0.2 and
+	/// `Some` otherwise.
+	pub counterparty_node_id: Option<PublicKey>,
 	/// The `channel_id` of the channel over which the HTLC was received.
 	pub channel_id: ChannelId,
 	/// The `user_channel_id` of the channel over which the HTLC was received. This is the value
@@ -263,6 +268,7 @@ impl_writeable_tlv_based!(ClaimedHTLC, {
 	(0, channel_id, required),
 	(1, counterparty_skimmed_fee_msat, (default_value, 0u64)),
 	(2, user_channel_id, required),
+	(3, counterparty_node_id, option),
 	(4, cltv_expiry, required),
 	(6, value_msat, required),
 });

lightning/src/ln/channelmanager.rs

@@ -512,6 +512,7 @@ struct ClaimableHTLC {
 impl From<&ClaimableHTLC> for events::ClaimedHTLC {
 	fn from(val: &ClaimableHTLC) -> Self {
 		events::ClaimedHTLC {
+			counterparty_node_id: val.prev_hop.counterparty_node_id,
 			channel_id: val.prev_hop.channel_id,
 			user_channel_id: val.prev_hop.user_channel_id.unwrap_or(0),
 			cltv_expiry: val.cltv_expiry,