Level B export: tags

Needs a new ActivityCsvPresenter method, because as previously seen
with `#sustainable_development_goals`, `ActivityPresenter#tags`
produces an HTML version.

app/presenters/activity_csv_presenter.rb

@@ -124,6 +124,14 @@ def sustainable_development_goals
     end
   end
 
+  def tags
+    return if self[:tags].blank?
+
+    tags_options.select { |tag| tag.code.in?(self[:tags]) }
+      .map(&:description)
+      .join("|")
+  end
+
   private
 
   def list_of_countries(country_code_list, klass)

spec/features/beis_users_can_download_exports_spec.rb

@@ -298,7 +298,7 @@
     other_fund_programme = create(:programme_activity, :newton_funded)
     programme_1 = create(
       :programme_activity, :ispf_funded, commitment: create(:commitment, value: BigDecimal("250_000.00")),
-      benefitting_countries: %w[AR EC BR]
+      benefitting_countries: %w[AR EC BR], tags: [4, 5]
     )
     programme_1.comments = create_list(:comment, 2)
     programme_1.budgets = [
@@ -351,7 +351,7 @@
         "Aid type" => "D01: Donor country personnel",
         "ODA eligibility" => "Eligible",
         "Publish to IATI?" => "Yes",
-        "Tags" => nil,
+        "Tags" => "Tactical Fund|Previously reported under OODA",
         "Budget 2023-2024" => "£101.00", # each revision adds £50 in the factories; we have 2
         "Budget 2024-2025" => "£2.00",
         "Budget 2025-2026" => nil,

spec/presenters/activity_csv_presenter_spec.rb

@@ -482,4 +482,18 @@
       it { is_expected.to be_nil }
     end
   end
+
+  describe "#tags" do
+    subject { described_class.new(activity).tags }
+
+    context "the activity has no tags" do
+      let(:activity) { build(:project_activity, tags: []) }
+      it { is_expected.to be_nil }
+    end
+
+    context "the activity has some tags from the codelist in tags.yml" do
+      let(:activity) { build(:project_activity, tags: [4, 5]) }
+      it { is_expected.to eql("Tactical Fund|Previously reported under OODA") }
+    end
+  end
 end