mod+itest: reproduce and fix reverse direction invoice payment

Fixes a bug that when an invoice is paid, the full invoice amount is
checked when validating the local channel balance and reserve. But for
custom channels the actual HTLC amount might be just above dust and
shouldn't validate the channel reserve.
We update our itest to reproduce the issue and then update to the lnd
commit that fixes it.

Author: guggero

go.mod

@@ -21,7 +21,7 @@ require (
 	github.com/lightninglabs/pool v0.6.5-beta.0.20240604070222-e121aadb3289
 	github.com/lightninglabs/pool/auctioneerrpc v1.1.2
 	github.com/lightninglabs/taproot-assets v0.4.0-alpha.rc3
-	github.com/lightningnetwork/lnd v0.18.0-beta.rc4.0.20240709210732-0cd11ad84792
+	github.com/lightningnetwork/lnd v0.18.0-beta.rc4.0.20240712025014-90f997c908d0
 	github.com/lightningnetwork/lnd/cert v1.2.2
 	github.com/lightningnetwork/lnd/fn v1.1.0
 	github.com/lightningnetwork/lnd/kvdb v1.4.8

go.sum

@@ -1179,8 +1179,8 @@ github.com/lightninglabs/taproot-assets v0.4.0-alpha.rc3 h1:Ovt4wMhCIqdw+uNwJaSf
 github.com/lightninglabs/taproot-assets v0.4.0-alpha.rc3/go.mod h1:oAiEnRj2sCbPHAURot+tmKbyDhIoxnvkmag0JqlF1bs=
 github.com/lightningnetwork/lightning-onion v1.2.1-0.20230823005744-06182b1d7d2f h1:Pua7+5TcFEJXIIZ1I2YAUapmbcttmLj4TTi786bIi3s=
 github.com/lightningnetwork/lightning-onion v1.2.1-0.20230823005744-06182b1d7d2f/go.mod h1:c0kvRShutpj3l6B9WtTsNTBUtjSmjZXbJd9ZBRQOSKI=
-github.com/lightningnetwork/lnd v0.18.0-beta.rc4.0.20240709210732-0cd11ad84792 h1:bM4UmjVTvhqwDCMzLZIDMecfo/mei4OS/BFLUzHiDNc=
-github.com/lightningnetwork/lnd v0.18.0-beta.rc4.0.20240709210732-0cd11ad84792/go.mod h1:L3IArArdRrWtuw+wNsUlibuGmf/08Odsm/zo3+bPXuM=
+github.com/lightningnetwork/lnd v0.18.0-beta.rc4.0.20240712025014-90f997c908d0 h1:V+PoltFSxN5oijkErYe+QbnVz5WJjBsAzaMNRrhmz3Q=
+github.com/lightningnetwork/lnd v0.18.0-beta.rc4.0.20240712025014-90f997c908d0/go.mod h1:L3IArArdRrWtuw+wNsUlibuGmf/08Odsm/zo3+bPXuM=
 github.com/lightningnetwork/lnd/cert v1.2.2 h1:71YK6hogeJtxSxw2teq3eGeuy4rHGKcFf0d0Uy4qBjI=
 github.com/lightningnetwork/lnd/cert v1.2.2/go.mod h1:jQmFn/Ez4zhDgq2hnYSw8r35bqGVxViXhX6Cd7HXM6U=
 github.com/lightningnetwork/lnd/clock v1.1.1 h1:OfR3/zcJd2RhH0RU+zX/77c0ZiOnIMsDIBjgjWdZgA0=

itest/litd_custom_channels_test.go

@@ -218,7 +218,7 @@ func testCustomChannels(_ context.Context, net *NetworkHarness,
 	// ------------
 	// Test case 1: Send a direct keysend payment from Charlie to Dave.
 	// ------------
-	const keySendAmount = 100
+	const keySendAmount = 1000
 	sendAssetKeySendPayment(
 		t.t, charlie, dave, keySendAmount, assetID, fn.None[int64](),
 	)
@@ -227,13 +227,13 @@ func testCustomChannels(_ context.Context, net *NetworkHarness,
 	charlieAssetBalance -= keySendAmount
 	daveAssetBalance += keySendAmount
 
-	// We should be able to send the 100 assets back immediately, because
+	// We should be able to send the 1000 assets back immediately, because
 	// there is enough on-chain balance on Dave's side to be able to create
-	// an HTLC.
-	sendAssetKeySendPayment(
-		t.t, dave, charlie, keySendAmount, assetID, fn.None[int64](),
+	// an HTLC. We use an invoice to execute another code path.
+	invoiceResp := createAssetInvoice(
+		t.t, dave, charlie, keySendAmount, assetID,
 	)
-	logBalance(t.t, nodes, assetID, "after keysend back")
+	payInvoiceWithAssets(t.t, dave, charlie, invoiceResp, assetID)
 
 	charlieAssetBalance += keySendAmount
 	daveAssetBalance -= keySendAmount
@@ -266,7 +266,7 @@ func testCustomChannels(_ context.Context, net *NetworkHarness,
 	// invoice.
 	// ------------
 	const daveInvoiceAssetAmount = 2_000
-	invoiceResp := createAssetInvoice(
+	invoiceResp = createAssetInvoice(
 		t.t, charlie, dave, daveInvoiceAssetAmount, assetID,
 	)
 	payInvoiceWithAssets(t.t, charlie, dave, invoiceResp, assetID)