Thread htlc hold time to monitor on fail

Recently, we began generating monitor events when HTLCs fail off-chain. In
upcoming commits, we'll begin relying on those events to resolve forwarded HTLC
fails on the inbound edge. As such, we need to thread the hold time to the
monitor so the generated event is correct.

Author: valentinewallace

lightning/src/ln/channel.rs

@@ -8789,7 +8789,7 @@ where
 					attribution_data: None,
 				};
 				mem::swap(outcome, &mut reason);
-				match reason {
+				match &mut reason {
 					OutboundHTLCOutcome::Success { preimage, .. } => {
 						// If a user (a) receives an HTLC claim using LDK 0.0.104 or before, then (b)
 						// upgrades to LDK 0.0.114 or later before the HTLC is fully resolved, we could
@@ -8799,11 +8799,16 @@ where
 						// claim anyway.
 						claimed_htlcs.push(OutboundHTLCClaim {
 							htlc_id: SentHTLCId::from_source(&htlc.source),
-							preimage,
+							preimage: *preimage,
 							skimmed_fee_msat: htlc.skimmed_fee_msat,
 						});
 					},
-					OutboundHTLCOutcome::Failure(ref fail_reason) => {
+					OutboundHTLCOutcome::Failure(fail_reason) => {
+						// The monitor needs the HTLC hold time to correctly resolve the HTLC when generating a
+						// monitor event for its failure.
+						hold_time_since(htlc.send_timestamp).map(|hold_time| {
+							fail_reason.set_hold_time(hold_time);
+						});
 						failed_htlcs.push(OutboundHTLCFail {
 							htlc_id: SentHTLCId::from_source(&htlc.source),
 							failure_reason: fail_reason.clone(),