I made this OAuth middleware for NodeJS a few years ago, but it can also act as an OAuth proxy, meaning that you can deploy the NodeJS app on your server and access it from another server written in any programming language.
Hi, this one was just to showcase my OAuth express middleware, which in turn uses a code from Mashape's guardian auth proxy.
Currently all of these OAuth flows requires human interaction, at least for the first time. I think the OAuth specs guys are working on a digital signature that will allow multiple provider sign on in future.
I made this OAuth middleware for NodeJS a few years ago, but it can also act as an OAuth proxy, meaning that you can deploy the NodeJS app on your server and access it from another server written in any programming language.
Here is the example app: https://grant.outofindex.com/