mulit: move payment query code to separate file

diff --git a/payments/db/kv_store.go b/payments/db/kv_store.go
index 0bd6576..02cce77 100644
--- a/payments/db/kv_store.go
+++ b/payments/db/kv_store.go
@@ -1131,9 +1131,9 @@ func fetchFailedHtlcKeys(bucket kvdb.RBucket) ([][]byte, error) {
 // to a subset of payments by the payments query, containing an offset
 // index and a maximum number of returned payments.
 func (p *KVPaymentsDB) QueryPayments(_ context.Context,
-	query PaymentsQuery) (PaymentsResponse, error) {
+	query Query) (Response, error) {
 
-	var resp PaymentsResponse
+	var resp Response
 
 	if err := kvdb.View(p.db, func(tx kvdb.RTx) error {
 		// Get the root payments bucket.
@@ -1247,7 +1247,7 @@ func (p *KVPaymentsDB) QueryPayments(_ context.Context,
 
 		return nil
 	}, func() {
-		resp = PaymentsResponse{}
+		resp = Response{}
 	}); err != nil {
 		return resp, err
 	}
diff --git a/payments/db/payment.go b/payments/db/payment.go
index a43e871..38948b1 100644
--- a/payments/db/payment.go
+++ b/payments/db/payment.go
@@ -19,74 +19,6 @@ import (
 	"github.com/lightningnetwork/lnd/routing/route"
 )
 
-// PaymentsQuery represents a query to the payments database starting or ending
-// at a certain offset index. The number of retrieved records can be limited.
-type PaymentsQuery struct {
-	// IndexOffset determines the starting point of the payments query and
-	// is always exclusive. In normal order, the query starts at the next
-	// higher (available) index compared to IndexOffset. In reversed order,
-	// the query ends at the next lower (available) index compared to the
-	// IndexOffset. In the case of a zero index_offset, the query will start
-	// with the oldest payment when paginating forwards, or will end with
-	// the most recent payment when paginating backwards.
-	IndexOffset uint64
-
-	// MaxPayments is the maximal number of payments returned in the
-	// payments query.
-	MaxPayments uint64
-
-	// Reversed gives a meaning to the IndexOffset. If reversed is set to
-	// true, the query will fetch payments with indices lower than the
-	// IndexOffset, otherwise, it will return payments with indices greater
-	// than the IndexOffset.
-	Reversed bool
-
-	// If IncludeIncomplete is true, then return payments that have not yet
-	// fully completed. This means that pending payments, as well as failed
-	// payments will show up if this field is set to true.
-	IncludeIncomplete bool
-
-	// CountTotal indicates that all payments currently present in the
-	// payment index (complete and incomplete) should be counted.
-	CountTotal bool
-
-	// CreationDateStart, expressed in Unix seconds, if set, filters out
-	// all payments with a creation date greater than or equal to it.
-	CreationDateStart int64
-
-	// CreationDateEnd, expressed in Unix seconds, if set, filters out all
-	// payments with a creation date less than or equal to it.
-	CreationDateEnd int64
-}
-
-// PaymentsResponse contains the result of a query to the payments database.
-// It includes the set of payments that match the query and integers which
-// represent the index of the first and last item returned in the series of
-// payments. These integers allow callers to resume their query in the event
-// that the query's response exceeds the max number of returnable events.
-type PaymentsResponse struct {
-	// Payments is the set of payments returned from the database for the
-	// PaymentsQuery.
-	Payments []*MPPayment
-
-	// FirstIndexOffset is the index of the first element in the set of
-	// returned MPPayments. Callers can use this to resume their query
-	// in the event that the slice has too many events to fit into a single
-	// response. The offset can be used to continue reverse pagination.
-	FirstIndexOffset uint64
-
-	// LastIndexOffset is the index of the last element in the set of
-	// returned MPPayments. Callers can use this to resume their query
-	// in the event that the slice has too many events to fit into a single
-	// response. The offset can be used to continue forward pagination.
-	LastIndexOffset uint64
-
-	// TotalCount represents the total number of payments that are currently
-	// stored in the payment database. This will only be set if the
-	// CountTotal field in the query was set to true.
-	TotalCount uint64
-}
-
 // HTLCAttemptInfo contains static information about a specific HTLC attempt
 // for a payment. This information is used by the router to handle any errors
 // coming back after an attempt is made, and to query the switch about the
diff --git a/payments/db/payment_test.go b/payments/db/payment_test.go
index 897f570..91cbdca 100644
--- a/payments/db/payment_test.go
+++ b/payments/db/payment_test.go
@@ -134,7 +134,7 @@ func TestQueryPayments(t *testing.T) {
 	// of legacy payments.
 	tests := []struct {
 		name       string
-		query      PaymentsQuery
+		query      Query
 		firstIndex uint64
 		lastIndex  uint64
 
@@ -144,7 +144,7 @@ func TestQueryPayments(t *testing.T) {
 	}{
 		{
 			name: "IndexOffset at the end of the payments range",
-			query: PaymentsQuery{
+			query: Query{
 				IndexOffset:       7,
 				MaxPayments:       7,
 				Reversed:          false,
@@ -156,7 +156,7 @@ func TestQueryPayments(t *testing.T) {
 		},
 		{
 			name: "query in forwards order, start at beginning",
-			query: PaymentsQuery{
+			query: Query{
 				IndexOffset:       0,
 				MaxPayments:       2,
 				Reversed:          false,
@@ -168,7 +168,7 @@ func TestQueryPayments(t *testing.T) {
 		},
 		{
 			name: "query in forwards order, start at end, overflow",
-			query: PaymentsQuery{
+			query: Query{
 				IndexOffset:       6,
 				MaxPayments:       2,
 				Reversed:          false,
@@ -180,7 +180,7 @@ func TestQueryPayments(t *testing.T) {
 		},
 		{
 			name: "start at offset index outside of payments",
-			query: PaymentsQuery{
+			query: Query{
 				IndexOffset:       20,
 				MaxPayments:       2,
 				Reversed:          false,
@@ -192,7 +192,7 @@ func TestQueryPayments(t *testing.T) {
 		},
 		{
 			name: "overflow in forwards order",
-			query: PaymentsQuery{
+			query: Query{
 				IndexOffset:       4,
 				MaxPayments:       math.MaxUint64,
 				Reversed:          false,
@@ -205,7 +205,7 @@ func TestQueryPayments(t *testing.T) {
 		{
 			name: "start at offset index outside of payments, " +
 				"reversed order",
-			query: PaymentsQuery{
+			query: Query{
 				IndexOffset:       9,
 				MaxPayments:       2,
 				Reversed:          true,
@@ -217,7 +217,7 @@ func TestQueryPayments(t *testing.T) {
 		},
 		{
 			name: "query in reverse order, start at end",
-			query: PaymentsQuery{
+			query: Query{
 				IndexOffset:       0,
 				MaxPayments:       2,
 				Reversed:          true,
@@ -229,7 +229,7 @@ func TestQueryPayments(t *testing.T) {
 		},
 		{
 			name: "query in reverse order, starting in middle",
-			query: PaymentsQuery{
+			query: Query{
 				IndexOffset:       4,
 				MaxPayments:       2,
 				Reversed:          true,
@@ -242,7 +242,7 @@ func TestQueryPayments(t *testing.T) {
 		{
 			name: "query in reverse order, starting in middle, " +
 				"with underflow",
-			query: PaymentsQuery{
+			query: Query{
 				IndexOffset:       4,
 				MaxPayments:       5,
 				Reversed:          true,
@@ -254,7 +254,7 @@ func TestQueryPayments(t *testing.T) {
 		},
 		{
 			name: "all payments in reverse, order maintained",
-			query: PaymentsQuery{
+			query: Query{
 				IndexOffset:       0,
 				MaxPayments:       7,
 				Reversed:          true,
@@ -266,7 +266,7 @@ func TestQueryPayments(t *testing.T) {
 		},
 		{
 			name: "exclude incomplete payments",
-			query: PaymentsQuery{
+			query: Query{
 				IndexOffset:       0,
 				MaxPayments:       7,
 				Reversed:          false,
@@ -278,7 +278,7 @@ func TestQueryPayments(t *testing.T) {
 		},
 		{
 			name: "query payments at index gap",
-			query: PaymentsQuery{
+			query: Query{
 				IndexOffset:       1,
 				MaxPayments:       7,
 				Reversed:          false,
@@ -290,7 +290,7 @@ func TestQueryPayments(t *testing.T) {
 		},
 		{
 			name: "query payments reverse before index gap",
-			query: PaymentsQuery{
+			query: Query{
 				IndexOffset:       3,
 				MaxPayments:       7,
 				Reversed:          true,
@@ -302,7 +302,7 @@ func TestQueryPayments(t *testing.T) {
 		},
 		{
 			name: "query payments reverse on index gap",
-			query: PaymentsQuery{
+			query: Query{
 				IndexOffset:       2,
 				MaxPayments:       7,
 				Reversed:          true,
@@ -314,7 +314,7 @@ func TestQueryPayments(t *testing.T) {
 		},
 		{
 			name: "query payments forward on index gap",
-			query: PaymentsQuery{
+			query: Query{
 				IndexOffset:       2,
 				MaxPayments:       2,
 				Reversed:          false,
@@ -327,7 +327,7 @@ func TestQueryPayments(t *testing.T) {
 		{
 			name: "query in forwards order, with start creation " +
 				"time",
-			query: PaymentsQuery{
+			query: Query{
 				IndexOffset:       0,
 				MaxPayments:       2,
 				Reversed:          false,
@@ -341,7 +341,7 @@ func TestQueryPayments(t *testing.T) {
 		{
 			name: "query in forwards order, with start creation " +
 				"time at end, overflow",
-			query: PaymentsQuery{
+			query: Query{
 				IndexOffset:       0,
 				MaxPayments:       2,
 				Reversed:          false,
@@ -354,7 +354,7 @@ func TestQueryPayments(t *testing.T) {
 		},
 		{
 			name: "query with start and end creation time",
-			query: PaymentsQuery{
+			query: Query{
 				IndexOffset:       9,
 				MaxPayments:       math.MaxUint64,
 				Reversed:          true,
diff --git a/payments/db/query.go b/payments/db/query.go
new file mode 100644
index 0000000..5904ab5
--- /dev/null
+++ b/payments/db/query.go
@@ -0,0 +1,69 @@
+package paymentsdb
+
+// Query represents a query to the payments database starting or ending
+// at a certain offset index. The number of retrieved records can be limited.
+type Query struct {
+	// IndexOffset determines the starting point of the payments query and
+	// is always exclusive. In normal order, the query starts at the next
+	// higher (available) index compared to IndexOffset. In reversed order,
+	// the query ends at the next lower (available) index compared to the
+	// IndexOffset. In the case of a zero index_offset, the query will start
+	// with the oldest payment when paginating forwards, or will end with
+	// the most recent payment when paginating backwards.
+	IndexOffset uint64
+
+	// MaxPayments is the maximal number of payments returned in the
+	// payments query.
+	MaxPayments uint64
+
+	// Reversed gives a meaning to the IndexOffset. If reversed is set to
+	// true, the query will fetch payments with indices lower than the
+	// IndexOffset, otherwise, it will return payments with indices greater
+	// than the IndexOffset.
+	Reversed bool
+
+	// If IncludeIncomplete is true, then return payments that have not yet
+	// fully completed. This means that pending payments, as well as failed
+	// payments will show up if this field is set to true.
+	IncludeIncomplete bool
+
+	// CountTotal indicates that all payments currently present in the
+	// payment index (complete and incomplete) should be counted.
+	CountTotal bool
+
+	// CreationDateStart, expressed in Unix seconds, if set, filters out
+	// all payments with a creation date greater than or equal to it.
+	CreationDateStart int64
+
+	// CreationDateEnd, expressed in Unix seconds, if set, filters out all
+	// payments with a creation date less than or equal to it.
+	CreationDateEnd int64
+}
+
+// Response contains the result of a query to the payments database.
+// It includes the set of payments that match the query and integers which
+// represent the index of the first and last item returned in the series of
+// payments. These integers allow callers to resume their query in the event
+// that the query's response exceeds the max number of returnable events.
+type Response struct {
+	// Payments is the set of payments returned from the database for the
+	// Query.
+	Payments []*MPPayment
+
+	// FirstIndexOffset is the index of the first element in the set of
+	// returned MPPayments. Callers can use this to resume their query
+	// in the event that the slice has too many events to fit into a single
+	// response. The offset can be used to continue reverse pagination.
+	FirstIndexOffset uint64
+
+	// LastIndexOffset is the index of the last element in the set of
+	// returned MPPayments. Callers can use this to resume their query
+	// in the event that the slice has too many events to fit into a single
+	// response. The offset can be used to continue forward pagination.
+	LastIndexOffset uint64
+
+	// TotalCount represents the total number of payments that are currently
+	// stored in the payment database. This will only be set if the
+	// CountTotal field in the query was set to true.
+	TotalCount uint64
+}
diff --git a/rpcserver.go b/rpcserver.go
index d26e4b8..8b4c1b1 100644
--- a/rpcserver.go
+++ b/rpcserver.go
@@ -7513,7 +7513,7 @@ func (r *rpcServer) ListPayments(ctx context.Context,
 		}
 	}
 
-	query := paymentsdb.PaymentsQuery{
+	query := paymentsdb.Query{
 		IndexOffset:       req.IndexOffset,
 		MaxPayments:       req.MaxPayments,
 		Reversed:          req.Reversed,