Merge branch 'rspec-csv-response-helper' into 'master'

Add CSV response helper for controller specs

See merge request gitlab-org/gitlab!39164

spec/support/csv_response.rb

+# frozen_string_literal: true
+
+RSpec.configure do |config|
+  config.include_context 'CSV response', type: :controller
+end

spec/support/shared_contexts/csv_response_shared_context.rb

+# frozen_string_literal: true
+
+RSpec.shared_context 'CSV response' do
+  let(:csv_response) { CSV.parse(response.body) }
+end