I'm nearing completion of a XenForo forum I've been working on, but there is one last thing in the way before I can deliver it. Currently I make use of an External API to keep the forum accounts up to date regarding e-mail, username, forum groups, banned status, etcetera. For this to work properly I have some additional read-only data to assign to an user (for example an userId used by the external API). I have been thinking about adding extra hidden uneditable user fields and store all data I might need in there, but that sounds a tad hackish. Are there any other ways? Perhaps through the authentication data or can I extend the User model and add extra database fields easily? I'm looking for the most clean solution, not particulary the easiest. Any kind of tip or thought is welcomed!