Added ability to use timestamp from devices message (if "ts" found in converter output dictionary.)

To use this feature, converted data structure must be like:
{
  "deviceName": "Device",
  "deviceType": "default",
  "attributes": [],
  "telemetry": {
    "ts": 1580214207748,
    "values": {
      "telemetry1": 400,
      "telemetry2": 200
    }
  }
}

thingsboard_gateway/gateway/tb_gateway_service.py

@@ -262,9 +262,16 @@ class TBGatewayService:
                 self.__connector_incoming_messages[connector_name] += 1
 
         telemetry = {}
+        telemetry_with_ts = []
         for item in data["telemetry"]:
-            telemetry = {**telemetry, **item}
+            if item.get("ts") is None:
-        data["telemetry"] = {"ts": int(time.time() * 1000), "values": telemetry}
+                telemetry = {**telemetry, **item}
+            else:
+                telemetry_with_ts.append({"ts": item["ts"], "values": {**item["values"]}})
+        if telemetry_with_ts:
+            data["telemetry"] = telemetry_with_ts
+        else:
+            data["telemetry"] = {"ts": int(time.time() * 1000), "values": telemetry}
 
         json_data = dumps(data)
         save_result = self._event_storage.put(json_data)

thingsboard_gateway/tb_utility/tb_utility.py

@@ -108,12 +108,17 @@ class TBUtility:
         full_value = None
         try:
             if value_type == "string":
-                full_value = expression[0: min(abs(p1 - 2), 0)] + body[target_str.split()[0]] + expression[p2 + 1:len(expression)]
+                try:
+                    full_value = expression[0: min(abs(p1 - 2), 0)] + body[target_str.split()[0]] + expression[p2 + 1:len(expression)]
+                except KeyError:
+                    pass
                 if full_value is None:
                     try:
                         full_value = search(expression, body).group(0)
                     except Exception as e:
                         full_value = None
+                if full_value is None:
+                    full_value = expression
             else:
                 try:
                     full_value = body.get(target_str.split()[0])