Adapt ActionStatus timestamp doc (#2130)

Co-authored-by: vasilchev <vasil.ilchev@bosch.com>

hawkbit-ddi/hawkbit-ddi-api/src/main/java/org/eclipse/hawkbit/ddi/json/model/DdiActionFeedback.java

@@ -47,7 +47,7 @@ import lombok.Data;
 @JsonIgnoreProperties(ignoreUnknown = true)
 public class DdiActionFeedback {
 
-    @Schema(description = "Timestamp of the action in milliseconds since epoch", example = "1627997501890")
+    @Schema(description = "Timestamp (in milliseconds) when this status change occurred on Device.", example = "1627997501890")
     private final Long timestamp;
 
     @NotNull

site/content/apis/dmf_api.md

@@ -180,7 +180,8 @@ is [ActionUpdateStatus](https://github.com/eclipse-hawkbit/hawkbit/tree/master/h
   "actionId": long,
   "softwareModuleId": long,
   "actionStatus":"String",
-  "message":["String"]
+  "message":["String"],
+  "timestamp": long
 }
 ```
 
@@ -210,7 +211,8 @@ Example header and payload:
   "actionId":137,
   "softwareModuleId":17,
   "actionStatus":"DOWNLOAD",
-  "message":["The download has started"]
+  "message":["The download has started"],
+  "timestamp": 1704070800000
 }
 ```
 
@@ -279,7 +281,8 @@ Example header and payload when cancellation is successful:
   "actionId":137,
   "softwareModuleId":17,
   "actionStatus":"CANCELED",
-  "message":["The update was canceled."]
+  "message":["The update was canceled."],
+  "timestamp": 1704070800000
 }
 ```
 
@@ -294,7 +297,8 @@ Example header and payload when cancellation is rejected:
   "actionId":137,
   "softwareModuleId":17,
   "actionStatus":"CANCEL_REJECTED",
-  "message":["The cancellation was not possible since the target sent an unexpected response."]
+  "message":["The cancellation was not possible since the target sent an unexpected response."],
+  "timestamp": 1704070800000
 }
 ```