define fields as optional instead of two different types

interfaces/SimpleScene/SimpleScene.proto

@@ -2,14 +2,7 @@ syntax = "proto3";
 
 message IposConfig {
     repeated IposFrame frame = 1;
-    repeated IposObject object = 2; // an object must be either in this list
-    repeated IposObjectConfig objectConfig = 3; // or in this list, not in both
-}
-
-message IposObjectConfig {
-    string id = 1; // unique for each object, but there may be multiple positioning sensors for that object
-    string sensorId = 2; // unique (each sensor localizes a single object)
-    string type = 3; // CeTI will send BOX,BIN,ZONE,ROBOT,HUMAN,OTHER
+    repeated IposObject object = 2;
 }
 
 message IposPositionUpdate {
@@ -17,12 +10,17 @@ message IposPositionUpdate {
 }
 
 message IposObject {
+
+  // required:
   string id = 1; // unique for each object, but there may be multiple sensors
   string sensorId = 2; // unique
   string type = 3; // Applications may send BOX,BIN,ZONE,ROBOT,HUMAN,OTHER
+
+  // optional:
   IposRelativePosition position = 4;
   IposSimpleOrientation orientation = 5;
   string lastPosUpdate = 6; // https://en.wikipedia.org/wiki/ISO_8601
+
 }
 
 message IposFrame {