Remove exports/base controller in favor of shared concern (#3444)

spec/controllers/concerns/export_controller_concern_spec.rb

@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe ApplicationController, type: :controller do
+  controller do
+    include ExportControllerConcern
+    def index
+      send_export_file
+    end
+    def export_data
+      @export.account.username
+    end
+  end
+
+  describe 'GET #index' do
+    it 'returns a csv of the exported data when signed in' do
+      user = Fabricate(:user)
+      sign_in user
+      get :index, format: :csv
+
+      expect(response).to have_http_status(:success)
+      expect(response.content_type).to eq 'text/csv'
+      expect(response.headers['Content-Disposition']).to eq 'attachment; filename="anonymous.csv"'
+      expect(response.body).to eq user.account.username
+    end
+
+    it 'returns unauthorized when not signed in' do
+      get :index, format: :csv
+      expect(response).to have_http_status(:unauthorized)
+    end
+  end
+end