multi: thread context through SendPayment

diff --git a/routing/router.go b/routing/router.go
index 71dcf7d..c0bc15c 100644
--- a/routing/router.go
+++ b/routing/router.go
@@ -896,8 +896,8 @@ func (l *LightningPayment) Identifier() [32]byte {
 // will be returned which describes the path the successful payment traversed
 // within the network to reach the destination. Additionally, the payment
 // preimage will also be returned.
-func (r *ChannelRouter) SendPayment(payment *LightningPayment) ([32]byte,
-	*route.Route, error) {
+func (r *ChannelRouter) SendPayment(ctx context.Context,
+	payment *LightningPayment) ([32]byte, *route.Route, error) {
 
 	paySession, shardTracker, err := r.PreparePayment(payment)
 	if err != nil {
@@ -908,7 +908,7 @@ func (r *ChannelRouter) SendPayment(payment *LightningPayment) ([32]byte,
 		spewPayment(payment))
 
 	return r.sendPayment(
-		context.Background(), payment.FeeLimit, payment.Identifier(),
+		ctx, payment.FeeLimit, payment.Identifier(),
 		payment.PayAttemptTimeout, paySession, shardTracker,
 		payment.FirstHopCustomRecords,
 	)
diff --git a/routing/router_test.go b/routing/router_test.go
index 9bc7bdb..f1c6c38 100644
--- a/routing/router_test.go
+++ b/routing/router_test.go
@@ -328,7 +328,9 @@ func TestSendPaymentRouteFailureFallback(t *testing.T) {
 
 	// Send off the payment request to the router, route through pham nuwen
 	// should've been selected as a fall back and succeeded correctly.
-	paymentPreImage, route, err := ctx.router.SendPayment(payment)
+	paymentPreImage, route, err := ctx.router.SendPayment(
+		t.Context(), payment,
+	)
 	require.NoErrorf(t, err, "unable to send payment: %v",
 		payment.paymentHash)
 
@@ -407,7 +409,9 @@ func TestSendPaymentRouteInfiniteLoopWithBadHopHint(t *testing.T) {
 
 	// Send off the payment request to the router, should succeed
 	// ignoring the bad channel id hint.
-	paymentPreImage, route, paymentErr := ctx.router.SendPayment(payment)
+	paymentPreImage, route, paymentErr := ctx.router.SendPayment(
+		t.Context(), payment,
+	)
 	require.NoErrorf(t, paymentErr, "unable to send payment: %v",
 		payment.paymentHash)
 
@@ -638,7 +642,9 @@ func TestSendPaymentErrorRepeatedFeeInsufficient(t *testing.T) {
 
 	// Send off the payment request to the router, route through phamnuwen
 	// should've been selected as a fall back and succeeded correctly.
-	paymentPreImage, route, err := ctx.router.SendPayment(payment)
+	paymentPreImage, route, err := ctx.router.SendPayment(
+		t.Context(), payment,
+	)
 	require.NoErrorf(t, err, "unable to send payment: %v",
 		payment.paymentHash)
 
@@ -745,7 +751,9 @@ func TestSendPaymentErrorFeeInsufficientPrivateEdge(t *testing.T) {
 
 	// Send off the payment request to the router, route through son
 	// goku and then across the private channel to elst.
-	paymentPreImage, route, err := ctx.router.SendPayment(payment)
+	paymentPreImage, route, err := ctx.router.SendPayment(
+		t.Context(), payment,
+	)
 	require.NoErrorf(t, err, "unable to send payment: %v",
 		payment.paymentHash)
 
@@ -871,7 +879,9 @@ func TestSendPaymentPrivateEdgeUpdateFeeExceedsLimit(t *testing.T) {
 
 	// Send off the payment request to the router, route through son
 	// goku and then across the private channel to elst.
-	paymentPreImage, route, err := ctx.router.SendPayment(payment)
+	paymentPreImage, route, err := ctx.router.SendPayment(
+		t.Context(), payment,
+	)
 	require.NoErrorf(t, err, "unable to send payment: %v",
 		payment.paymentHash)
 
@@ -994,7 +1004,9 @@ func TestSendPaymentErrorNonFinalTimeLockErrors(t *testing.T) {
 	// Send off the payment request to the router, this payment should
 	// succeed as we should actually go through Pham Nuwen in order to get
 	// to Sophon, even though he has higher fees.
-	paymentPreImage, rt, err := ctx.router.SendPayment(payment)
+	paymentPreImage, rt, err := ctx.router.SendPayment(
+		t.Context(), payment,
+	)
 	require.NoErrorf(t, err, "unable to send payment: %v",
 		payment.paymentHash)
 
@@ -1020,7 +1032,9 @@ func TestSendPaymentErrorNonFinalTimeLockErrors(t *testing.T) {
 	// w.r.t to the block height, and instead go through Pham Nuwen. We
 	// flip a bit in the payment hash to allow resending this payment.
 	payment.paymentHash[1] ^= 1
-	paymentPreImage, rt, err = ctx.router.SendPayment(payment)
+	paymentPreImage, rt, err = ctx.router.SendPayment(
+		t.Context(), payment,
+	)
 	require.NoErrorf(t, err, "unable to send payment: %v",
 		payment.paymentHash)
 
@@ -1089,7 +1103,7 @@ func TestSendPaymentErrorPathPruning(t *testing.T) {
 
 	// When we try to dispatch that payment, we should receive an error as
 	// both attempts should fail and cause both routes to be pruned.
-	_, _, err = ctx.router.SendPayment(payment)
+	_, _, err = ctx.router.SendPayment(t.Context(), payment)
 	require.Error(t, err, "payment didn't return error")
 
 	// The final error returned should also indicate that the peer wasn't
@@ -1134,7 +1148,9 @@ func TestSendPaymentErrorPathPruning(t *testing.T) {
 	// This shouldn't return an error, as we'll make a payment attempt via
 	// the pham nuwen channel based on the assumption that there might be an
 	// intermittent issue with the songoku <-> sophon channel.
-	paymentPreImage, rt, err := ctx.router.SendPayment(payment)
+	paymentPreImage, rt, err := ctx.router.SendPayment(
+		t.Context(), payment,
+	)
 	require.NoErrorf(t, err, "unable to send payment: %v",
 		payment.paymentHash)
 
@@ -1174,7 +1190,9 @@ func TestSendPaymentErrorPathPruning(t *testing.T) {
 
 	// We flip a bit in the payment hash to allow resending this payment.
 	payment.paymentHash[1] ^= 1
-	paymentPreImage, rt, err = ctx.router.SendPayment(payment)
+	paymentPreImage, rt, err = ctx.router.SendPayment(
+		t.Context(), payment,
+	)
 	require.NoErrorf(t, err, "unable to send payment: %v",
 		payment.paymentHash)
 
@@ -1306,7 +1324,7 @@ func TestUnknownErrorSource(t *testing.T) {
 	// the route a->b->c is tried first. An unreadable faiure is returned
 	// which should pruning the channel a->b. We expect the payment to
 	// succeed via a->d.
-	_, _, err = ctx.router.SendPayment(payment)
+	_, _, err = ctx.router.SendPayment(t.Context(), payment)
 	require.NoErrorf(t, err, "unable to send payment: %v",
 		payment.paymentHash)
 
@@ -1331,7 +1349,7 @@ func TestUnknownErrorSource(t *testing.T) {
 	// Send off the payment request to the router. We expect the payment to
 	// fail because both routes have been pruned.
 	payment.paymentHash[1] ^= 1
-	_, _, err = ctx.router.SendPayment(payment)
+	_, _, err = ctx.router.SendPayment(t.Context(), payment)
 	if err == nil {
 		t.Fatalf("expected payment to fail")
 	}
diff --git a/rpcserver.go b/rpcserver.go
index 3909fb1..c40d973 100644
--- a/rpcserver.go
+++ b/rpcserver.go
@@ -6022,7 +6022,7 @@ func (r *rpcServer) dispatchPaymentIntent(ctx context.Context,
 		}
 
 		preImage, route, routerErr = r.server.chanRouter.SendPayment(
-			payment,
+			ctx, payment,
 		)
 	} else {
 		var attempt *paymentsdb.HTLCAttempt