paymentsdb: add subsystem logging for payments package

diff --git a/log.go b/log.go
index 49ee5af..2484a35 100644
--- a/log.go
+++ b/log.go
@@ -46,6 +46,7 @@ import (
 	"github.com/lightningnetwork/lnd/monitoring"
 	"github.com/lightningnetwork/lnd/msgmux"
 	"github.com/lightningnetwork/lnd/netann"
+	paymentsdb "github.com/lightningnetwork/lnd/payments/db"
 	"github.com/lightningnetwork/lnd/peer"
 	"github.com/lightningnetwork/lnd/peernotifier"
 	"github.com/lightningnetwork/lnd/protofsm"
@@ -207,6 +208,10 @@ func SetupLoggers(root *build.SubLoggerManager, interceptor signal.Interceptor)
 	AddSubLogger(root, chainio.Subsystem, interceptor, chainio.UseLogger)
 	AddSubLogger(root, msgmux.Subsystem, interceptor, msgmux.UseLogger)
 	AddSubLogger(root, sqldb.Subsystem, interceptor, sqldb.UseLogger)
+	AddSubLogger(
+		root, paymentsdb.Subsystem, interceptor, paymentsdb.UseLogger,
+	)
+
 }
 
 // AddSubLogger is a helper method to conveniently create and register the
diff --git a/payments/db/log.go b/payments/db/log.go
new file mode 100644
index 0000000..08994ef
--- /dev/null
+++ b/payments/db/log.go
@@ -0,0 +1,34 @@
+package paymentsdb
+
+import (
+	"github.com/btcsuite/btclog/v2"
+	"github.com/lightningnetwork/lnd/build"
+)
+
+// log is a logger that is initialized with no output filters.  This
+// means the package will not perform any logging by default until the caller
+// requests it.
+//
+//nolint:unused
+var log btclog.Logger
+
+// Subsystem defines the logging identifier for this subsystem.
+const Subsystem = "PYDB"
+
+// The default amount of logging is none.
+func init() {
+	UseLogger(build.NewSubLogger(Subsystem, nil))
+}
+
+// DisableLog disables all library log output.  Logging output is disabled
+// by default until UseLogger is called.
+func DisableLog() {
+	UseLogger(btclog.Disabled)
+}
+
+// UseLogger uses a specified Logger to output package logging info.
+// This should be used in preference to SetLogWriter if the caller is also
+// using btclog.
+func UseLogger(logger btclog.Logger) {
+	log = logger
+}