itest: expect failure on direct rfq peer btc invoice

Previously we'd consider it acceptable to settle direct rfq peer
invoices, which included no rfq scid, with asset HTLCs. This behavior
has been updated on the tapd invoice manager and we no longer accept
asset HTLCs on invoices that do not expect assets. This commit updates
such payments in our itests to instead expect a failure.

itest/litd_custom_channels_test.go

@@ -482,14 +482,12 @@ func testCustomChannels(_ context.Context, net *NetworkHarness,
 	// a direct channel invoice payment with no RFQ SCID present in the
 	// invoice.
 	// ------------
-	paidAssetAmount := createAndPayNormalInvoice(
+	createAndPayNormalInvoice(
 		t.t, charlie, dave, dave, 20_000, assetID, withSmallShards(),
+		withFailure(lnrpc.Payment_FAILED, failureIncorrectDetails),
 	)
 	logBalance(t.t, nodes, assetID, "after invoice")
 
-	charlieAssetBalance -= paidAssetAmount
-	daveAssetBalance += paidAssetAmount
-
 	// We should also be able to do a multi-hop BTC only payment, paying an
 	// invoice from Erin by Charlie.
 	createAndPayNormalInvoiceWithBtc(t.t, charlie, erin, 2000)
@@ -535,7 +533,7 @@ func testCustomChannels(_ context.Context, net *NetworkHarness,
 	// ------------
 	// Test case 4: Pay a normal invoice from Erin by Charlie.
 	// ------------
-	paidAssetAmount = createAndPayNormalInvoice(
+	paidAssetAmount := createAndPayNormalInvoice(
 		t.t, charlie, dave, erin, 20_000, assetID, withSmallShards(),
 	)
 	logBalance(t.t, nodes, assetID, "after invoice")
@@ -921,14 +919,12 @@ func testCustomChannelsGroupedAsset(_ context.Context, net *NetworkHarness,
 	// a direct channel invoice payment with no RFQ SCID present in the
 	// invoice.
 	// ------------
-	paidAssetAmount := createAndPayNormalInvoice(
+	createAndPayNormalInvoice(
 		t.t, charlie, dave, dave, 20_000, assetID, withSmallShards(),
+		withFailure(lnrpc.Payment_FAILED, failureIncorrectDetails),
 	)
 	logBalance(t.t, nodes, assetID, "after invoice")
 
-	charlieAssetBalance -= paidAssetAmount
-	daveAssetBalance += paidAssetAmount
-
 	// We should also be able to do a multi-hop BTC only payment, paying an
 	// invoice from Erin by Charlie.
 	createAndPayNormalInvoiceWithBtc(t.t, charlie, erin, 2000)
@@ -966,7 +962,7 @@ func testCustomChannelsGroupedAsset(_ context.Context, net *NetworkHarness,
 	// ------------
 	// Test case 4: Pay a normal invoice from Erin by Charlie.
 	// ------------
-	paidAssetAmount = createAndPayNormalInvoice(
+	paidAssetAmount := createAndPayNormalInvoice(
 		t.t, charlie, dave, erin, 20_000, assetID, withSmallShards(),
 	)
 	logBalance(t.t, nodes, assetID, "after invoice")
@@ -1960,17 +1956,6 @@ func testCustomChannelsLiquidityEdgeCases(ctxb context.Context,
 		t.t, charlie, invoiceResp.RHash, assetID, bigAssetAmount,
 	)
 
-	// Edge case: Big normal invoice, paid by direct channel peer with
-	// assets.
-	const hugeAssetAmount = 1_000_000
-	_ = createAndPayNormalInvoice(
-		t.t, dave, charlie, charlie, hugeAssetAmount, assetID,
-		withSmallShards(),
-	)
-
-	logBalance(t.t, nodes, assetID, "after big asset payment (btc "+
-		"invoice, direct)")
-
 	// Dave sends 200k assets and 5k sats to Yara.
 	sendAssetKeySendPayment(
 		t.t, dave, yara, 2*bigAssetAmount, assetID, fn.None[int64](),