Add schema markup to breadcrumb

What does this MR do?

This MR adds schema markup for breadcrumbs. It adds it using ld+json because the breadcrumb generation logic is so intricate that it's really messy to introduce the microdata tags.

Refs #36844 (closed)

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 #36844 (closed)

app/helpers/breadcrumbs_helper.rb

@@ -12,7 +12,7 @@ def add_to_breadcrumbs(text, link)
   def breadcrumb_title_link
     return @breadcrumb_link if @breadcrumb_link
 
-    request.path
+    "#{request.base_url}#{request.path}"
   end
 
   def breadcrumb_title(title)
@@ -32,4 +32,31 @@ def add_to_breadcrumb_dropdown(link, location: :before)
     @breadcrumb_dropdown_links[location] ||= []
     @breadcrumb_dropdown_links[location] << link
   end
+
+  def push_to_schema_breadcrumb(text, link)
+    schema_breadcrumb_list.push(schema_list_item(text, link, schema_breadcrumb_list.size + 1))
+  end
+
+  def schema_breadcrumb_json
+    {
+      '@context': 'https://schema.org',
+      '@type': 'BreadcrumbList',
+      'itemListElement': schema_breadcrumb_list
+    }.to_json
+  end
+
+  private
+
+  def schema_breadcrumb_list
+    @schema_breadcrumb_list ||= []
+  end
+
+  def schema_list_item(text, link, position)
+    {
+      '@type' => 'ListItem',
+      'position' => position,
+      'name' => text,
+      'item' => link
+    }
+  end
 end