Introduce action status scoped custom code (#1277)

* Allow providing a custom code with an action status feedback to give more fine grained device specific details.
* Add ddi rest docs for new optional status code value.
* Provide new code value via mgmt api. Fix review findings.
* Fix failing tests

Signed-off-by: Michael Herdt <Michael.Herdt@bosch.io>
Co-authored-by: Stefan Behl <stefan.behl@bosch.io>

hawkbit-rest/hawkbit-mgmt-resource/src/main/java/org/eclipse/hawkbit/mgmt/rest/resource/MgmtTargetMapper.java

@@ -299,6 +299,7 @@ public final class MgmtTargetMapper {
         result.setReportedAt(actionStatus.getCreatedAt());
         result.setStatusId(actionStatus.getId());
         result.setType(actionStatus.getStatus().name().toLowerCase());
+        actionStatus.getCode().ifPresent(result::setCode);
 
         return result;
     }