fix: Fix Portlet preloading URL and Crossorigin - Meeds-io/meeds#2483 (…

…#234)

Prior to this change, the URL to preload when displaying the page is
different from the loaded fetch call using JS services of the page
layout. In addition, the crossorigin attribute has to be the same as the
fetch call 'credentials' attribute which is with value 'include'.

Resolves Meeds-io/meeds#2483

layout-webapp/src/main/webapp/groovy/portal/webui/container/UIPageLayout.gtmpl

@@ -18,7 +18,7 @@
       def portletId = portlets.get(i).getId();
       if (portletId != null) {
         %>
-        <link rel="prefetch" as="fetch" type="text/html" href="<%=rcontext.getRequest().getRequestURI()%>?maximizedPortletId<%=portletId%>&showMaxWindow=true&hideSharedLayout=true&maximizedPortletMode=VIEW" crossorigin><%
+        <link rel="preload" as="fetch" href="<%=rcontext.getRequest().getRequestURI()%>?maximizedPortletId=<%=portletId%>&showMaxWindow=true&hideSharedLayout=true&maximizedPortletMode=VIEW" crossorigin="use-credentials"><%
       }
     }
   }