Add banner to the schemes page

app/views/organisations/schemes.html.erb

@@ -11,6 +11,16 @@
   ) %>
   <h2 class="govuk-visually-hidden">Supported housing schemes</h2>
 <% end %>
+
+<% if display_duplicate_schemes_banner?(@organisation, current_user) %>
+  <%= govuk_notification_banner(title_text: "Important") do %>
+    <p class="govuk-notification-banner__heading govuk-!-width-full" style="max-width: fit-content">
+      Some schemes and locations might be duplicates.
+    <p>
+    <%= govuk_link_to "Review possible duplicates", href: schemes_duplicates_organisation_path(@organisation) %>
+  <% end %>
+<% end %>
+
 <div class="app-filter-layout" data-controller="filter-layout">
   <% if SchemePolicy.new(current_user, nil).create? %>
     <%= govuk_button_link_to "Create a new supported housing scheme", new_scheme_path, html: { method: :post } %>

config/routes.rb

@@ -178,6 +178,7 @@ Rails.application.routes.draw do
       get "schemes/csv-download", to: "organisations#download_schemes_csv"
       post "schemes/email-csv", to: "organisations#email_schemes_csv"
       get "schemes/csv-confirmation", to: "schemes#csv_confirmation"
+      get "schemes/duplicates", to: "organisations#duplicate_schemes"
       get "stock-owners", to: "organisation_relationships#stock_owners"
       get "stock-owners/add", to: "organisation_relationships#add_stock_owner"
       get "stock-owners/remove", to: "organisation_relationships#remove_stock_owner"

spec/requests/organisations_controller_spec.rb

@@ -207,6 +207,24 @@ RSpec.describe OrganisationsController, type: :request do
             expect(page).to have_title("#{user.organisation.name} (1 scheme matching ‘#{search_param}’) - Submit social housing lettings and sales data (CORE) - GOV.UK")
           end
         end
+
+        context "when organisation has absorbed other organisations" do
+          before do
+            create(:organisation, merge_date: Time.zone.today, absorbing_organisation: organisation)
+          end
+
+          context "and it has duplicate schemes or locations" do
+            before do
+              create_list(:scheme, 2, :duplicate, owning_organisation: organisation)
+              get "/organisations/#{organisation.id}/schemes", headers:, params: {}
+            end
+
+            it "displays a banner with correct content" do
+              expect(page).to have_content("Some schemes and locations might be duplicates.")
+              expect(page).to have_link("Review possible duplicates", href: "/organisations/#{organisation.id}/schemes/duplicates")
+            end
+          end
+        end
       end
 
       context "when data coordinator user" do