Added manual pages to last mod tracking (#4383)

* Added manual pages to last mod tracking

* Move manual pages to their own method and stub this in the tests to be empty

* Moved manual pages to a constant

lib/page_modification_tracker.rb

@@ -2,6 +2,12 @@
 require "digest/sha1"
 
 class PageModificationTracker
+  MANUAL_PAGES = {
+    "/events/about-get-into-teaching-events" => {},
+    "/events" => {},
+    "/mailinglist/signup/name" => {},
+  }.freeze
+
   attr_reader :app, :headers
 
   def initialize(host: "localhost:3000", selector: "body")
@@ -49,7 +55,7 @@ def published_pages
     )
     content_pages = ::Pages::Frontmatter.list.reject { |_path, fm| fm[:draft] }
     event_pages = events.map { |e| Rails.application.routes.url_helpers.event_path(e.readable_id) }.index_with({})
-    content_pages.merge(event_pages)
+    content_pages.merge(**event_pages, **MANUAL_PAGES)
   end
 
   def request_path(path, app, headers)

spec/lib/page_modification_tracker_spec.rb

@@ -29,6 +29,8 @@
       .to receive(:search_teaching_events)
       .and_return([])
 
+    stub_const("PageModificationTracker::MANUAL_PAGES", {})
+
     allow(::Pages::Frontmatter)
       .to receive(:list)
       .and_return({ path => { draft: false } })