routing: persist mission control data

lnrpc/routerrpc/config.go

@@ -24,4 +24,8 @@ type RoutingConfig struct {
 	// executing a payment attempt that fails. It is used to trade off
 	// potentially better routes against their probability of succeeding.
 	AttemptCost btcutil.Amount `long:"attemptcost" description:"The (virtual) cost in sats of a failed payment attempt"`
+
+	// MaxMcHistory defines the maximum number of payment results that
+	// are held on disk by mission control.
+	MaxMcHistory int `long:"maxmchistory" description:"the maximum number of payment results that are held on disk by mission control"`
 }