Enum specifying how actions with user input forms, such as requesting re-review, are handled.

USER_INPUT_ACTION_RENDERING_OPTION_UNSPECIFIED Default value. Will never be provided by the API.
REDIRECT_TO_MERCHANT_CENTER Actions that require user input are represented only as links that points merchant to Merchant Center where they can request the action. Provides easier to implement alternative to BUILT_IN_USER_INPUT_ACTIONS.
BUILT_IN_USER_INPUT_ACTIONS Returns content and input form definition for each complex action. Your application needs to display this content and input form to the merchant before they can request processing of the action. To start the action, your application needs to call the triggeraction method.