Add cache config for configuration comparison (#5812)

cmd/config-current.go

@@ -139,6 +139,8 @@ func (s *serverConfig) ConfigDiff(t *serverConfig) string {
 		return "Domain configuration differs"
 	case s.StorageClass != t.StorageClass:
 		return "StorageClass configuration differs"
+	case !reflect.DeepEqual(s.Cache, t.Cache):
+		return "Cache configuration differs"
 	case !reflect.DeepEqual(s.Notify.AMQP, t.Notify.AMQP):
 		return "AMQP Notification configuration differs"
 	case !reflect.DeepEqual(s.Notify.NATS, t.Notify.NATS):

cmd/config-versions.go

@@ -580,7 +580,10 @@ type serverConfigV22 struct {
 	Notify notifier `json:"notify"`
 }
 
-// serverConfigV23 is just like version '22' with addition of cache field
+// serverConfigV23 is just like version '22' with addition of cache field.
+//
+// IMPORTANT NOTE: When updating this struct make sure that
+// serverConfig.ConfigDiff() is updated as necessary.
 type serverConfigV23 struct {
 	Version string `json:"version"`