Make schema breadcrumb urls absolute

What does this MR do?

In !46991 (merged) we include the logic to create the schema markup for breadcrumbs. For that we use the same info we use to build the regular HTML breadcrumb, including the link. These links are usually relative ones.

Although it's not totally certain, it seems tools that check schema markup, like the Google one, indicates that the url is invalid because it's relative.

In this MR we ensure to convert all relative links to absolute ones when creating the schema markup for the breadcrumb.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Separation of EE specific content

Related to #281378 (closed)

app/helpers/breadcrumbs_helper.rb

@@ -71,7 +71,16 @@ def schema_list_item(text, link, position)
       '@type' => 'ListItem',
       'position' => position,
       'name' => text,
-      'item' => link
+      'item' => ensure_absolute_link(link)
     }
   end
+
+  def ensure_absolute_link(link)
+    return "#{request.base_url}#{request.path}" if link.blank?
+
+    url = URI.parse(link)
+    url.absolute? ? link : URI.join(request.base_url, link).to_s
+  rescue URI::InvalidURIError
+    "#{request.base_url}#{request.path}"
+  end
 end