Resolve "Update highscores"

Closes #6 (closed)

backend/api/highscores.js

@@ -53,10 +53,10 @@ router.post("/highscore", (req, res) => {
 
       db.collection(collection).updateOne(
         {
-          gameid: req.body.gameid,
-          userid: req.body.userid
+          gameid: mongo.ObjectID(req.body.gameid),
+          userid: mongo.ObjectID(req.body.userid)
         },
-        { $set: { value: parseInt(req.body.score) } },
+        { $max: { value: req.body.value } },
         { upsert: true },
         (err, result) => {
           if (err) {