Add key attribute to policy

components/device-mgt/io.entgra.device.mgt.core.device.mgt.common/src/main/java/io/entgra/device/mgt/core/device/mgt/common/policy/mgt/ui/Policy.java

@@ -30,6 +30,7 @@ public class Policy {
     private String description;
     private String name;
     private List<Feature> features;
+    private String key;
 
     @XmlElement(name = "Description", required = true)
     public String getDescription() {
@@ -58,4 +59,13 @@ public class Policy {
     public void setFeatures(List<Feature> features) {
         this.features = features;
     }
+
+    @XmlAttribute(name = "key", required = false)
+    public String getKey() {
+        return key;
+    }
+
+    public void setKey(String key) {
+        this.key = key;
+    }
 }