Fix some compile warnings (#2919)

* Fix some compile warnings
* Some classes made final
* JPA entities made not serializable

Signed-off-by: Avgustin Marinov <Avgustin.Marinov@bosch.com>

hawkbit-mgmt/hawkbit-mgmt-api/src/main/java/org/eclipse/hawkbit/mgmt/json/model/distributionset/MgmtActionId.java

@@ -43,7 +43,7 @@ import org.springframework.hateoas.RepresentationModel;
              }
           }
         }""")
-public class MgmtActionId extends RepresentationModel<MgmtActionId> {
+public final class MgmtActionId extends RepresentationModel<MgmtActionId> {
 
     @Schema(description = "ID of the action")
     private long id;

hawkbit-mgmt/hawkbit-mgmt-api/src/main/java/org/eclipse/hawkbit/mgmt/json/model/target/MgmtDistributionSetAssignments.java

@@ -24,7 +24,7 @@ import lombok.NoArgsConstructor;
  */
 @NoArgsConstructor
 @JsonDeserialize(using = MgmtDistributionSetAssignmentsDeserializer.class)
-public class MgmtDistributionSetAssignments extends ArrayList<MgmtDistributionSetAssignment> {
+public final class MgmtDistributionSetAssignments extends ArrayList<MgmtDistributionSetAssignment> {
 
     @Serial
     private static final long serialVersionUID = 1L;
@@ -39,16 +39,6 @@ public class MgmtDistributionSetAssignments extends ArrayList<MgmtDistributionSe
         add(assignment);
     }
 
-    /**
-     * Constructor for an object that contains multiple distribution set
-     * assignments
-     *
-     * @param assignments the assignments
-     */
-    public MgmtDistributionSetAssignments(final List<MgmtDistributionSetAssignment> assignments) {
-        super(assignments);
-    }
-
     @Override
     @JsonIgnore
     public boolean isEmpty() {

hawkbit-mgmt/hawkbit-mgmt-api/src/main/java/org/eclipse/hawkbit/mgmt/rest/api/MgmtTargetRestApi.java

@@ -308,7 +308,7 @@ public interface MgmtTargetRestApi {
     @Operation(summary = "Controls (confirm/deny) actions waiting for confirmation", description = """
             Either confirm or deny an action which is waiting for confirmation.
             The action will be transferred into the RUNNING state in case confirming it.
-            The action will remain in WAITING_FOR_CONFIRMATION state in case denying it. 
+            The action will remain in WAITING_FOR_CONFIRMATION state in case denying it.
             Required Permission: READ_REPOSITORY AND UPDATE_TARGET
             """)
     @PutNoContentResponses