Update taxonomy topic email signup button

When a document collection is tagged to a level one taxon,
we want the email signup link to send the user to the confirmation page
instead of the select subtopics page.

app/views/content_items/document_collection.html.erb

@@ -22,11 +22,7 @@
 </div>
 
 <%= render 'shared/publisher_metadata_with_logo' %>
-<% if @content_item.taxonomy_topic_email_override_base_path.present? %>
-  <%= render 'shared/taxon_signup_link', base_path: @content_item.taxonomy_topic_email_override_base_path %>
-<% else %>
-  <%= render 'shared/single_page_notification_button', content_item: @content_item, skip_account: "true" %>
-<% end %>
+<%= render 'shared/document_collections_email_signup', content_item: @content_item %>
 
 <div class="govuk-grid-row">
   <div class="govuk-grid-column-two-thirds">

app/views/shared/_document_collections_email_signup.html.erb

@@ -0,0 +1,21 @@
+<% if @content_item.taxonomy_topic_email_override_base_path.present? %>
+  <div
+    data-module="ga4-link-tracker"
+    data-ga4-link='{ "event_name": "navigation", "type": "subscribe", "index": { "index_link": 1 }, "index_total": 1, "section": "Top" }'
+    data-ga4-track-links-only
+  >
+    <%= render "govuk_publishing_components/components/signup_link", {
+      link_text: "Get emails about this topic",
+      link_href: "/email-signup/confirm?topic=#{@content_item.taxonomy_topic_email_override_base_path}",
+      data: {
+        "module": "gem-track-click",
+        "track-category": "emailAlertLinkClicked",
+        "track-action": @content_item.taxonomy_topic_email_override_base_path,
+        "track-label": ""
+      },
+      margin_bottom: 6
+    } %>
+  </div>
+<% else %>
+  <%= render 'shared/single_page_notification_button', content_item: @content_item, skip_account: "true" %>
+<% end %>

test/integration/document_collection_test.rb

@@ -157,11 +157,13 @@ class DocumentCollectionTest < ActionDispatch::IntegrationTest
   test "renders with the single page notification button" do
     setup_and_visit_content_item("document_collection")
     assert page.has_css?(".gem-c-single-page-notification-button")
+    assert_not page.has_css?(".gem-c-signup-link")
   end
 
   test "renders with the taxonomy subscription button" do
     setup_and_visit_content_item_with_taxonomy_topic_email_override("document_collection")
     assert page.has_css?(".gem-c-signup-link")
+    assert page.has_link?(href: "/email-signup/confirm?topic=/testpath")
     assert_not page.has_css?(".gem-c-single-page-notification-button")
   end
 end

test/test_helper.rb

@@ -198,7 +198,7 @@ def setup_and_visit_content_item_with_taxons(name, taxons)
   def setup_and_visit_content_item_with_taxonomy_topic_email_override(name)
     @content_item = get_content_example(name).tap do |item|
       item["links"]["taxonomy_topic_email_override"] = [{
-        "base_path": "test",
+        "base_path": "/testpath",
       }]
       stub_content_store_has_item(item["base_path"], item.to_json)
       visit_with_cachebust(item["base_path"])