Add copy constructor in stakeholder class.

src/main/java/eu/dnetlib/uoamonitorservice/entities/Stakeholder.java

@@ -17,6 +17,10 @@ public class Stakeholder extends StakeholderGeneric<String> {
         super();
     }
 
+    public Stakeholder(Stakeholder stakeholder) {
+        super(stakeholder);
+    }
+
     public Stakeholder(StakeholderFull stakeholder) {
         super(stakeholder);
         this.topics = stakeholder.getTopics().stream().map(Common::getId).collect(Collectors.toList());