multi: move payment related code into own package

This commit moves most of the code into its own package. It is
the smallest code move possible without moving import cycles and
keeping the changes to the code base as small as possible during
refactor.

lnrpc/routerrpc/router_server.go

@@ -15,7 +15,6 @@ import (
 	"github.com/btcsuite/btcd/wire"
 	"github.com/grpc-ecosystem/grpc-gateway/v2/runtime"
 	"github.com/lightningnetwork/lnd/aliasmgr"
-	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/fn/v2"
 	"github.com/lightningnetwork/lnd/lnrpc"
 	"github.com/lightningnetwork/lnd/lnrpc/invoicesrpc"
@@ -927,7 +926,7 @@ func (s *Server) SendToRouteV2(ctx context.Context,
 		return nil, err
 	}
 
-	var attempt *channeldb.HTLCAttempt
+	var attempt *paymentsdb.HTLCAttempt
 
 	// Pass route to the router. This call returns the full htlc attempt
 	// information as it is stored in the database. It is possible that both
@@ -1449,17 +1448,17 @@ func (s *Server) trackPaymentStream(context context.Context,
 				// No more payment updates.
 				return nil
 			}
-			result := item.(*channeldb.MPPayment)
+			result := item.(*paymentsdb.MPPayment)
 
 			log.Tracef("Payment %v updated to state %v",
 				result.Info.PaymentIdentifier, result.Status)
 
 			// Skip in-flight updates unless requested.
 			if noInflightUpdates {
-				if result.Status == channeldb.StatusInitiated {
+				if result.Status == paymentsdb.StatusInitiated {
 					continue
 				}
-				if result.Status == channeldb.StatusInFlight {
+				if result.Status == paymentsdb.StatusInFlight {
 					continue
 				}
 			}