Add option to request partial accounts in grouped notifications API (#31299)

spec/requests/api/v2_alpha/notifications_spec.rb

@@ -160,6 +160,36 @@ RSpec.describe 'Notifications' do
       end
     end
 
+    context 'when requesting stripped-down accounts' do
+      let(:params) { { expand_accounts: 'partial_avatars' } }
+
+      let(:recent_account) { Fabricate(:account) }
+
+      before do
+        FavouriteService.new.call(recent_account, user.account.statuses.first)
+      end
+
+      it 'returns an account in "partial_accounts", with the expected keys', :aggregate_failures do
+        subject
+
+        expect(response).to have_http_status(200)
+        expect(body_as_json[:partial_accounts].size).to be > 0
+        expect(body_as_json[:partial_accounts][0].keys).to contain_exactly(:acct, :avatar, :avatar_static, :bot, :id, :locked, :url)
+        expect(body_as_json[:partial_accounts].pluck(:id)).to_not include(recent_account.id.to_s)
+        expect(body_as_json[:accounts].pluck(:id)).to include(recent_account.id.to_s)
+      end
+    end
+
+    context 'when passing an invalid value for "expand_accounts"' do
+      let(:params) { { expand_accounts: 'unknown_foobar' } }
+
+      it 'returns http bad request' do
+        subject
+
+        expect(response).to have_http_status(400)
+      end
+    end
+
     def body_json_types
       body_as_json[:notification_groups].pluck(:type)
     end