This method is specific to everyauth (because it uses `this.Promise()`, which tightly couples you to that authentication medium.  You should create a generic method here that has a signature `findOrCreateUser(githubUser, callback)` or even better `findOrCreateUser(githubUser) => Promise` then inline an anonymous function for everyauth that handles the specific API that everyauth expects.

Failing that, at least mark this method as being everyauth specific.