I think I've done it....
I think I've got a recreation of Alby's auth and one end point so far.
You need to have a Hive account and the only endpoint I've built is
/user/value4value
Once you get a bearer token, that end point will return details for the hive user who completed log in. Details of the two URLs which need to change are in this gist:
https://gist.github.com/brianoflondon/dfb6e9f4d38ee2c776b8b707f3e89dc9