Auth0 UUID Rule

function (user, context, callback) {
   var uuid = require("uuid");
 
   user.app_metadata = user.app_metadata || {};
 
   var promise = Promise.resolve(1);
 
   if (!user.app_metadata.uuid) {
     user.app_metadata.uuid = uuid();
 
     promise = auth0.users.updateAppMetadata(user.user_id, user.app_metadata);
   }
 
   promise.then(() => {
     if (context.idToken) {
       // Include the uuid in the issued ID token if applicable
       context.idToken["http://kobu.io/uuid"] = user.app_metadata.uuid;
     }
 
     if (context.accessToken) {
       // Include the uuid in the issued access token if applicable
       context.accessToken["http://kobu.io/uuid"] = user.app_metadata.uuid;
     }
     
     callback(null, user, context);
   }).catch(callback);
 }