This repository can be deployed as a GitHub Pages Page and used as a redirect URL for Spotify Developer Applications. The only thing it will do is show you all the information Spotify is returning for you to work with. This might be helpful if you want to play around with the spotify api and don't yet have a mechanism in place which handles the output of the spotify login form inside your App.
I was working with Workflow for iOS (Shourtcuts since iOS 12) and I wasn't able to find a way to handle the authorization codes inside of Workflow so I had to let the user work with the codes and enter them manually into the Workflow. This is definitely not a good UX and should be avoided but that's the best I could do in Workflow.