As described in our documentation (here) the process for engaging with a third-party Authorization Server varies. So sadly we don’t provide code examples or the like for doing this. Third parties often build SDKs that can help - the googleapis SDK for Node.js being a good example of one which takes care of automatically refreshing any tokens too. However, if you just have to engage for token refresh, then it typically will be a whole lot easier as you will typically just need to call the equivalent /token endpoint as opposed to doing the whole /authorize dance too 
2 Likes