Add request id parameter

rmf_charger_msgs/msg/ChargerCancel.msg

@@ -1 +1,6 @@
 string charger_name  # the charger that should process this message
+
+# A unique ID for each request. It is advised that you prefix this
+# with the sender's node name. This is used for error tracking
+# later on
+string request_id

rmf_charger_msgs/msg/ChargerRequest.msg

@@ -9,3 +9,8 @@ string robot_name
 # If the robot takes longer than this to arrive and start charging,
 # the charge request will be canceled.
 builtin_interfaces/Duration start_timeout
+
+# A unique ID for each request. It is advised that you prefix this
+# with the sender's node name. This is used for error tracking
+# later on
+string request_id

rmf_charger_msgs/msg/ChargerState.msg

@@ -1,21 +1,25 @@
-# time when this state message was created
+# Time when this state message was created
 builtin_interfaces/Time charger_time
 
 uint32 CHARGER_IDLE = 1      # Charger is not occupied
 uint32 CHARGER_ASSIGNED = 2  # Charger has been assigned a robot
 uint32 CHARGER_CHARGING = 3  # Charger is charging
 uint32 CHARGER_ERROR = 200   # Error state, see error_message for info
 
-uint32 state         # One of the previously enumerated states
+uint32 state  # One of the previously enumerated states
 
-# the charger name should be unique in the RMF system and
+# The charger name should be unique in the RMF system and
 # should match a charger name appearing in the traffic map
 string charger_name
 
-# the error_message field should be blank unless state is CHARGER_ERROR
+# The error_message field should be blank unless state is CHARGER_ERROR
 string error_message
 
-# the robot that is currently assigned to this charger (if any)
+# The request_id field will be populated with the ID that started the
+# charging cycle if state is anything other than CHARGER_IDLE
+string request_id
+
+# The robot that is currently assigned to this charger (if any)
 string robot_fleet
 string robot_name