Refactor favoriting a badge to class method

controllers/backpack.js

@@ -100,17 +100,14 @@ module.exports = function (app) {
     var data = req.remote;
     var badge = data.badge;
     var user = res.locals.user;
+    var shortName = req.params.id; // assume if we got here id is valid input
 
-    favorite.findOrCreate({
-      type: 'badge',
-      itemId: req.params.id, // assume if we got here id is valid input
-      LearnerId: user.id
-    }).complete(function(err, fav) {
+    favorite.favoriteBadge(user, shortName, function(err, fav) {
         if (err) {
             return next(err);
         }
         res.render('user/badge-favorited.html', {
-          badge: badge
+            badge: badge
         });
     });
   });

models/favorite.js

@@ -26,5 +26,17 @@ module.exports = {
 			model: 'Learner',
 			type: 'belongsTo'
 		}
-	]
+	],
+  classMethods: {
+		// favoriteBadge adds a badge to the list of a user's favorites
+		favoriteBadge: function (user, shortName, callback) {
+			this.create({type: 'badge', itemId: shortName, LearnerId: user.id}).
+				success(function(fav) {
+					callback(null, fav);
+				}).
+				error(function(err) {
+					callback(err);
+				});
+		}
+	}
 };