Fix : The related item in the item preview is not updated [SDESK-6830] (

#4204)

* Fix : The related item in the item preview is not updated [SDESK-6830]

* fix lint

* create a throttle function to avoid fire a network request on any property change

scripts/apps/archive/directives/RelatedItemsPreview.ts

@@ -1,6 +1,7 @@
 import {IArticle, IArticleField, IRendition} from 'superdesk-api';
 import {gettext} from 'core/utils';
 import {getThumbnailForItem} from 'core/helpers/item';
+import {throttle} from 'lodash';
 
 /**
  * @ngdoc directive
@@ -38,11 +39,19 @@ export function RelatedItemsPreview(relationsService) {
             scope.gettext = gettext;
             scope.getThumbnailForItem = getThumbnailForItem;
 
-            relationsService.getRelatedItemsForField(scope.item, scope.field._id)
-                .then((items) => {
-                    scope.relatedItems = items;
-                    scope.loading = false;
-                });
+            // Define the throttled function
+            const getRelatedItems = throttle((item) => {
+                relationsService.getRelatedItemsForField(item, scope.field._id)
+                    .then((items) => {
+                        scope.relatedItems = items;
+                        scope.loading = false;
+                    });
+            }, 1000);
+
+            scope.$watch('item', (item) => {
+                scope.loading = true;
+                getRelatedItems(item);
+            });
         },
     };
 }