fix(modalContainer): See modalContainer asset on add in editor (#2700)

Covers [UID-34](https://bonitasoft.atlassian.net/browse/UID-34)

frontend/app/js/editor/whiteboard/whiteboard-component-wrapper.service.js

@@ -146,7 +146,7 @@
         $$propertiesTemplateUrl: 'js/editor/properties-panel/modal-container-properties-template.html',
         $$parentContainerRow: parentRow,
         triggerRemoved: whiteboardService.onRemoveModalContainer.bind(null, element),
-        triggerAdded: angular.noop
+        triggerAdded: whiteboardService.onAddModalContainer.bind(null, element),
       });
       service.wrapContainer({ id: 'pbContainer' }, element.container);
       return component;

frontend/app/js/editor/whiteboard/whiteboard.service.js

@@ -22,6 +22,7 @@
       onRemoveContainer: onRemoveContainer,
       onRemoveTabsContainer: onRemoveTabsContainer,
       onAddTabsContainer,
+      onAddModalContainer,
       onRemoveTab: onRemoveTab,
       onRemoveFormContainer: onRemoveFormContainer,
       onRemoveModalContainer: onRemoveModalContainer,
@@ -82,6 +83,10 @@
       executeFunctionsForComponent(onWidgetAddFunctions, tabsContainer);
     }
 
+    function onAddModalContainer(modalContainer) {
+      executeFunctionsForComponent(onWidgetAddFunctions, modalContainer);
+    }
+
     function onRemoveTabsContainer(tabsContainer) {
       tabsContainer.tabs.forEach(onRemoveTab);
       executeFunctionsForComponent(onWidgetRemoveFunctions, tabsContainer);