multi: create channeldb/models package

Add a new subpackage to `lnd/channeldb` to hold some of the types that
are used in the package itself and in other packages that should not
depend on `channeldb`.

contractcourt/interfaces.go

@@ -5,6 +5,7 @@ import (
 
 	"github.com/btcsuite/btcd/wire"
 	"github.com/lightningnetwork/lnd/channeldb"
+	"github.com/lightningnetwork/lnd/channeldb/models"
 	"github.com/lightningnetwork/lnd/htlcswitch/hop"
 	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/invoices"
@@ -27,7 +28,7 @@ type Registry interface {
 	// the resolution is sent on the passed in hodlChan later.
 	NotifyExitHopHtlc(payHash lntypes.Hash, paidAmount lnwire.MilliSatoshi,
 		expiry uint32, currentHeight int32,
-		circuitKey channeldb.CircuitKey, hodlChan chan<- interface{},
+		circuitKey models.CircuitKey, hodlChan chan<- interface{},
 		payload invoices.Payload) (invoices.HtlcResolution, error)
 
 	// HodlUnsubscribeAll unsubscribes from all htlc resolutions.
@@ -70,6 +71,6 @@ type UtxoSweeper interface {
 type HtlcNotifier interface {
 	// NotifyFinalHtlcEvent notifies the HtlcNotifier that the final outcome
 	// for an htlc has been determined.
-	NotifyFinalHtlcEvent(key channeldb.CircuitKey,
+	NotifyFinalHtlcEvent(key models.CircuitKey,
 		info channeldb.FinalHtlcInfo)
 }