I have an app that's using Linkedin api. I can successfully log a user in to linkedin and retrieve info, but I would like to save something from their profile so they have a unique ID in my rails api Users table. I've read the userID from linkedin can possibly change if the API key for the app changes for any reason. Is using that id still the best way of registering a new user in my app or is some other unique private info more suitable?
You are correct that the member id value is unique to the user + application. Do you plan on changing your application key? If not, then that should be the id that you use. I can't think of a good reason that you would typically change your application key.