channeldb: add HtlcIndex to HTLCEntry

This may be useful for custom channel types that base everything off the index (a global value) rather than the output index (can change with each state).

channeldb/revocation_log_test.go

@@ -59,10 +59,13 @@ var (
 		CustomBlob: tlv.SomeRecordT(
 			tlv.NewPrimitiveRecord[tlv.TlvType5](blobBytes),
 		),
+		HtlcIndex: tlv.SomeRecordT(
+			tlv.NewPrimitiveRecord[tlv.TlvType6, uint16](0x33),
+		),
 	}
 	testHTLCEntryBytes = []byte{
-		// Body length 41.
-		0x29,
+		// Body length 45.
+		0x2d,
 		// Rhash tlv.
 		0x0, 0x0,
 		// RefundTimeout tlv.
@@ -76,6 +79,8 @@ var (
 		// Custom blob tlv.
 		0x5, 0x11, 0xfe, 0x00, 0x01, 0x00, 0x01, 0x0b, 0x63, 0x75, 0x73,
 		0x74, 0x6f, 0x6d, 0x20, 0x64, 0x61, 0x74, 0x61,
+		// HLTC index tlv.
+		0x6, 0x2, 0x0, 0x33,
 	}
 
 	testHTLCEntryHash = HTLCEntry{
@@ -126,7 +131,11 @@ var (
 		Htlcs: []HTLC{{
 			RefundTimeout: testHTLCEntry.RefundTimeout.Val,
 			OutputIndex:   int32(testHTLCEntry.OutputIndex.Val),
-			Incoming:      testHTLCEntry.Incoming.Val,
+			HtlcIndex: uint64(
+				testHTLCEntry.HtlcIndex.ValOpt().
+					UnsafeFromSome(),
+			),
+			Incoming: testHTLCEntry.Incoming.Val,
 			Amt: lnwire.NewMSatFromSatoshis(
 				testHTLCEntry.Amt.Val.Int(),
 			),
@@ -294,7 +303,7 @@ func TestSerializeHTLCEntries(t *testing.T) {
 	partialBytes := testHTLCEntryBytes[3:]
 
 	// Write the total length and RHash tlv.
-	expectedBytes := []byte{0x49, 0x0, 0x20}
+	expectedBytes := []byte{0x4d, 0x0, 0x20}
 	expectedBytes = append(expectedBytes, rHashBytes...)
 
 	// Append the rest.