Use edition links for worldwide organisation offices

We are switching worldwide organisations to use edition links which do
not support multi-level link expanstion.

Therefore we need to switch the rendering code to use the new link
fields that have been added, in the absence of multi-level links.

This change adds support for edition links, but also retains
compatibility with non-edition links. This will allow us to deploy the
frontend changes in advance of republishing the content items,
preventing any downtime of these pages. The code for backward
compatibility will be removed once the content items have all been
republished with edition links.

app/presenters/worldwide_organisation_presenter.rb

@@ -86,7 +86,13 @@ def people_in_non_primary_roles
 
   def main_office
     return unless (office_item = content_item.dig("links", "main_office")&.first)
-    return unless (office_contact_item = office_item.dig("links", "contact")&.first)
+
+    office_contact_item = if office_item.dig("links", "contact")
+                            office_item.dig("links", "contact")&.first # To be removed once switched to edition links
+                          else
+                            contact_for_office(office_item["content_id"])
+                          end
+    return unless office_contact_item
 
     WorldwideOffice.new(
       contact: WorldwideOrganisation::LinkedContactPresenter.new(office_contact_item),
@@ -101,7 +107,12 @@ def home_page_offices
     return [] unless content_item.dig("links", "home_page_offices")
 
     content_item.dig("links", "home_page_offices").map { |office|
-      next unless (contact = office.dig("links", "contact")&.first)
+      contact = if office.dig("links", "contact")
+                  office.dig("links", "contact")&.first # To be removed once switched to edition links
+                else
+                  contact_for_office(office["content_id"])
+                end
+      next unless contact
 
       WorldwideOrganisation::LinkedContactPresenter.new(contact)
     }.compact
@@ -136,6 +147,18 @@ def sponsoring_organisations
 
 private
 
+  def contact_for_office(office_content_id)
+    contact_mapping = content_item.dig("details", "office_contact_associations").select { |office_contact_association|
+      office_contact_association["office_content_id"] == office_content_id
+    }.first
+
+    return unless contact_mapping
+
+    content_item.dig("links", "contacts").select { |contact|
+      contact["content_id"] == contact_mapping["contact_content_id"]
+    }.first
+  end
+
   def presented_title_for_roles(roles)
     roles
       .map { |role| role["title"] }