server+lncfg: make sweepr batch window duration configurable

lncfg/sweeper.go

@@ -0,0 +1,19 @@
+package lncfg
+
+import (
+	"fmt"
+	"time"
+)
+
+type Sweeper struct {
+	BatchWindowDuration time.Duration `long:"batchwindowduration" description:"Duration of the sweep batch window. The sweep is held back during the batch window to allow more inputs to be added and thereby lower the fee per input."`
+}
+
+// Validate checks the values configured for the sweeper.
+func (s *Sweeper) Validate() error {
+	if s.BatchWindowDuration < 0 {
+		return fmt.Errorf("batchwindowduration must be positive")
+	}
+
+	return nil
+}