invoices: integrate settlement interceptor with invoice registry

This commit updates the invoice registry to utilize the settlement
interceptor during the invoice settlement routine. It allows the
interceptor to capture the invoice, providing interception clients an
opportunity to determine the settlement outcome.

invoices/invoiceregistry_test.go

@@ -23,6 +23,12 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+var (
+	// htlcModifierMock is a mock implementation of the invoice HtlcModifier
+	// interface.
+	htlcModifierMock = &invpkg.MockHtlcModifier{}
+)
+
 // TestInvoiceRegistry is a master test which encompasses all tests using an
 // InvoiceDB instance. The purpose of this test is to be able to run all tests
 // with a custom DB instance, so that we can test the same logic with different
@@ -517,6 +523,7 @@ func testSettleHoldInvoice(t *testing.T,
 	cfg := invpkg.RegistryConfig{
 		FinalCltvRejectDelta: testFinalCltvRejectDelta,
 		Clock:                clock,
+		HtlcInterceptor:      htlcModifierMock,
 	}
 
 	expiryWatcher := invpkg.NewInvoiceExpiryWatcher(
@@ -683,6 +690,7 @@ func testCancelHoldInvoice(t *testing.T,
 	cfg := invpkg.RegistryConfig{
 		FinalCltvRejectDelta: testFinalCltvRejectDelta,
 		Clock:                testClock,
+		HtlcInterceptor:      htlcModifierMock,
 	}
 	expiryWatcher := invpkg.NewInvoiceExpiryWatcher(
 		cfg.Clock, 0, uint32(testCurrentHeight), nil, newMockNotifier(),
@@ -1200,6 +1208,7 @@ func testInvoiceExpiryWithRegistry(t *testing.T,
 	cfg := invpkg.RegistryConfig{
 		FinalCltvRejectDelta: testFinalCltvRejectDelta,
 		Clock:                testClock,
+		HtlcInterceptor:      htlcModifierMock,
 	}
 
 	expiryWatcher := invpkg.NewInvoiceExpiryWatcher(
@@ -1310,6 +1319,7 @@ func testOldInvoiceRemovalOnStart(t *testing.T,
 		FinalCltvRejectDelta:        testFinalCltvRejectDelta,
 		Clock:                       testClock,
 		GcCanceledInvoicesOnStartup: true,
+		HtlcInterceptor:             htlcModifierMock,
 	}
 
 	expiryWatcher := invpkg.NewInvoiceExpiryWatcher(