Disallow EPP domain:update/transfer/delete if a domain has "deleteCandidate" status

#355

spec/models/concerns/domain/deletable_spec.rb

@@ -0,0 +1,17 @@
+require 'rails_helper'
+
+RSpec.describe Domain, db: false do
+  describe '#discarded?' do
+    context 'when :deleteCandidate status is present' do
+      let(:domain) { described_class.new(statuses: [DomainStatus::DELETE_CANDIDATE]) }
+
+      specify { expect(domain).to be_discarded }
+    end
+
+    context 'when :deleteCandidate status is absent' do
+      let(:domain) { described_class.new(statuses: []) }
+
+      specify { expect(domain).to_not be_discarded }
+    end
+  end
+end