multi: break invoice depenency on channeldb

Now that we have the new package `lnd/channeldb/models` we can invert the
depenency between `channeldb` and `invoices`.

- Move all the invoice related types and errors to the
`invoices` package.

- Ensure that all the packages dealing with invoices use the types and
  interfaces defined in the `invoices` package.

- Implement the InvoiceDB interface (defined in `lnd/invoices`) in
  channeldb.

- Add new mock for InterfaceDB.

- `InvoiceRegistery` tests are now in its own subpacakge (they need to
  import both invoices & channeldb). This is temporary until we can
  decouple them.

lnrpc/invoicesrpc/utils.go

@@ -6,7 +6,7 @@ import (
 
 	"github.com/btcsuite/btcd/btcec/v2"
 	"github.com/btcsuite/btcd/chaincfg"
-	"github.com/lightningnetwork/lnd/channeldb"
+	"github.com/lightningnetwork/lnd/invoices"
 	"github.com/lightningnetwork/lnd/lnrpc"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/zpay32"
@@ -16,7 +16,7 @@ import (
 // because not all information is stored in dedicated invoice fields. If there
 // is no payment request present, a dummy request will be returned. This can
 // happen with just-in-time inserted keysend invoices.
-func decodePayReq(invoice *channeldb.Invoice,
+func decodePayReq(invoice *invoices.Invoice,
 	activeNetParams *chaincfg.Params) (*zpay32.Invoice, error) {
 
 	paymentRequest := string(invoice.PaymentRequest)
@@ -40,8 +40,8 @@ func decodePayReq(invoice *channeldb.Invoice,
 	return decoded, nil
 }
 
-// CreateRPCInvoice creates an *lnrpc.Invoice from the *channeldb.Invoice.
-func CreateRPCInvoice(invoice *channeldb.Invoice,
+// CreateRPCInvoice creates an *lnrpc.Invoice from the *invoices.Invoice.
+func CreateRPCInvoice(invoice *invoices.Invoice,
 	activeNetParams *chaincfg.Params) (*lnrpc.Invoice, error) {
 
 	decoded, err := decodePayReq(invoice, activeNetParams)
@@ -76,18 +76,22 @@ func CreateRPCInvoice(invoice *channeldb.Invoice,
 	satAmt := invoice.Terms.Value.ToSatoshis()
 	satAmtPaid := invoice.AmtPaid.ToSatoshis()
 
-	isSettled := invoice.State == channeldb.ContractSettled
+	isSettled := invoice.State == invoices.ContractSettled
 
 	var state lnrpc.Invoice_InvoiceState
 	switch invoice.State {
-	case channeldb.ContractOpen:
+	case invoices.ContractOpen:
 		state = lnrpc.Invoice_OPEN
-	case channeldb.ContractSettled:
+
+	case invoices.ContractSettled:
 		state = lnrpc.Invoice_SETTLED
-	case channeldb.ContractCanceled:
+
+	case invoices.ContractCanceled:
 		state = lnrpc.Invoice_CANCELED
-	case channeldb.ContractAccepted:
+
+	case invoices.ContractAccepted:
 		state = lnrpc.Invoice_ACCEPTED
+
 	default:
 		return nil, fmt.Errorf("unknown invoice state %v",
 			invoice.State)
@@ -97,11 +101,11 @@ func CreateRPCInvoice(invoice *channeldb.Invoice,
 	for key, htlc := range invoice.Htlcs {
 		var state lnrpc.InvoiceHTLCState
 		switch htlc.State {
-		case channeldb.HtlcStateAccepted:
+		case invoices.HtlcStateAccepted:
 			state = lnrpc.InvoiceHTLCState_ACCEPTED
-		case channeldb.HtlcStateSettled:
+		case invoices.HtlcStateSettled:
 			state = lnrpc.InvoiceHTLCState_SETTLED
-		case channeldb.HtlcStateCanceled:
+		case invoices.HtlcStateCanceled:
 			state = lnrpc.InvoiceHTLCState_CANCELED
 		default:
 			return nil, fmt.Errorf("unknown state %v", htlc.State)
@@ -139,7 +143,7 @@ func CreateRPCInvoice(invoice *channeldb.Invoice,
 		}
 
 		// Only report resolved times if htlc is resolved.
-		if htlc.State != channeldb.HtlcStateAccepted {
+		if htlc.State != invoices.HtlcStateAccepted {
 			rpcHtlc.ResolveTime = htlc.ResolveTime.Unix()
 		}
 
@@ -182,11 +186,11 @@ func CreateRPCInvoice(invoice *channeldb.Invoice,
 
 		var state lnrpc.InvoiceHTLCState
 		switch ampState.State {
-		case channeldb.HtlcStateAccepted:
+		case invoices.HtlcStateAccepted:
 			state = lnrpc.InvoiceHTLCState_ACCEPTED
-		case channeldb.HtlcStateSettled:
+		case invoices.HtlcStateSettled:
 			state = lnrpc.InvoiceHTLCState_SETTLED
-		case channeldb.HtlcStateCanceled:
+		case invoices.HtlcStateCanceled:
 			state = lnrpc.InvoiceHTLCState_CANCELED
 		default:
 			return nil, fmt.Errorf("unknown state %v", ampState.State)
@@ -202,7 +206,7 @@ func CreateRPCInvoice(invoice *channeldb.Invoice,
 		// If at least one of the present HTLC sets show up as being
 		// settled, then we'll mark the invoice itself as being
 		// settled.
-		if ampState.State == channeldb.HtlcStateSettled {
+		if ampState.State == invoices.HtlcStateSettled {
 			rpcInvoice.Settled = true // nolint:staticcheck
 			rpcInvoice.State = lnrpc.Invoice_SETTLED
 		}