chainntnfs: add unique ID field to track conf ntfns within notifier

chainntnfs/bitcoindnotify/bitcoind.go

@@ -54,6 +54,7 @@ type chainUpdate struct {
 // chain client. Multiple concurrent clients are supported. All notifications
 // are achieved via non-blocking sends on client channels.
 type BitcoindNotifier struct {
+	confClientCounter  uint64 // To be used atomically.
 	spendClientCounter uint64 // To be used atomically.
 	epochClientCounter uint64 // To be used atomically.
 
@@ -716,6 +717,7 @@ func (b *BitcoindNotifier) RegisterConfirmationsNtfn(txid *chainhash.Hash,
 
 	ntfn := &confirmationNotification{
 		ConfNtfn: chainntnfs.ConfNtfn{
+			ConfID:           atomic.AddUint64(&b.confClientCounter, 1),
 			TxID:             txid,
 			NumConfirmations: numConfs,
 			Event:            chainntnfs.NewConfirmationEvent(numConfs),