code: def options_call
        OmniAuth.config.before_options_phase.call(env) if OmniAuth.config.before_options_phase
        verbs = OmniAuth.config.allowed_request_methods.collect(&:to_s).collect(&:upcase).join(', ')
        [200, {'Allow' => verbs}, []]
      end
docs: Responds to an OPTIONS request.