Add rake task to mark an organisation as closed

The `OrganisationFetcher` does not handle the situation of an
organisation having been deleted in Whitehall without first being
closed.

This means a deleted organisation remains marked as open, and can have
users assigned to it in Signon.

Adding a rake task to manually mark organisations as closed, in the
event this occurs again, so the organisation no longer appears as an
option to which users can be assigned in the user interface.

lib/tasks/data_hygiene.rake

@@ -5,4 +5,11 @@ namespace :data_hygiene do
       abort "bulk updating organisations encountered errors"
     end
   end
+
+  desc "Mark an organisation as closed"
+  task :close_organisation, %i[content_id] => :environment do |_, args|
+    organisation = Organisation.find_by(content_id: args[:content_id])
+    organisation.update!(closed: true)
+    puts "Marked organisation #{organisation.slug} as closed"
+  end
 end

test/lib/tasks/data_hygiene_test.rb

@@ -0,0 +1,19 @@
+require "test_helper"
+
+class DataHygieneTaskTest < ActiveSupport::TestCase
+  setup do
+    Signon::Application.load_tasks if Rake::Task.tasks.empty?
+
+    $stdout.stubs(:write)
+  end
+
+  context "#close_organisation" do
+    should "mark the organisation as closed" do
+      organisation = create(:organisation, slug: "department-of-health", closed: false)
+
+      Rake::Task["data_hygiene:close_organisation"].invoke(organisation.content_id)
+
+      assert organisation.reload.closed?
+    end
+  end
+end