LIBDRUM-912. Added "External Link to Data Files" to simple item page

Added an "External Link to Data Files" field in the left column of
the simple item page, which displays the value of the "dc.relation.uri"
metadata field.

https://umd-dit.atlassian.net/browse/LIBDRUM-912

Author: dsteelma-umd

src/assets/i18n/en.json5

@@ -7200,6 +7200,8 @@
 
   "item.page.doi": "DRUM DOI",
 
+  "item.page.externalDataFilesLink": "External Link to Data Files",
+
   "item.page.publicationLink": "Publication or External Link",
 
   "item.page.publicationLink.datasetOrSoftware": "Related Publication Link",

src/themes/drum/app/item-page/simple/item-types/untyped-item/untyped-item.component.html

@@ -41,6 +41,12 @@ <h2 class="item-page-title-field mr-auto">
       [label]="publicationLinkLabelI18nKey">
     </ds-item-page-uri-field>
 
+    <!-- External Link to Data Files -->
+    <ds-item-page-uri-field [item]="object"
+      [fields]="['dc.relation.uri']"
+      [label]="'item.page.externalDataFilesLink'">
+    </ds-item-page-uri-field>
+
     <!-- Date -->
     <ds-item-page-date-field [item]="object"></ds-item-page-date-field>