I need to integrate a back end application (i.e. without a GUI) with Magento 2 REST APIs. As such I believe I need to use OAuth for authentication. However, as it is a back end service, there will be no users to process any redirects to third party urls. Is it possible to authenticate via OAuth in Magento2 without going to a callback URL? I note when you register an integration the callbacks are optional, and if you leave them blank the access token and access token secret are generated. Many thanks.