Add a comment to clarify using metric samples in SensorData

Signed-off-by: Tiyash Basu <[email protected]>

Author: tiyash-basu-frequenz

proto/frequenz/api/common/v1/microgrid/sensors/sensors.proto

@@ -206,6 +206,10 @@ message SensorData {
   uint64 sensor_id = 1;
 
   // List of measurements for a metric of the specific microgrid sensor.
+  //
+  // Note that these metric samples will not necessarily contain bounds, since
+  // bounds are required for control operations, which are not applicable to
+  // sensors.
   repeated frequenz.api.common.v1.metrics.MetricSample metric_samples = 2;
 
   // List of states of a specific microgrid sensor.