lib/omniauth/strategy.rb
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
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
Responds to an OPTIONS request.