display full doi url not just the doi as a link

src/Plugin/Field/FieldFormatter/DoiFieldFormatter.php

@@ -41,8 +41,9 @@ class DoiFieldFormatter extends FormatterBase {
 
     foreach ($items as $delta => $item) {
       $prefix = 'https://doi.org/';
+      // Assumes all field values are just plain text or strings values and not full doi URLS.
       $doiUrl = $prefix . $item->value;
-      $link = Link::fromTextAndUrl($item->value, Url::fromUri($doiUrl));
+      $link = Link::fromTextAndUrl($doiUrl, Url::fromUri($doiUrl));
       $element[$delta] = [$link->toRenderable()];
     }
     return $element;