Resolve "As a QR-scanning connoisseur , I want to unlock stickers after scanning a QR code to feel a sense of reward."

Closes #73 (closed)

src/main/java/team5/smartTowns/rewards/Pack.java

+package team5.smartTowns.rewards;
+
+import lombok.Getter;
+
+import java.util.List;
+
+@Getter
+public class Pack extends Reward{
+
+    int progression; //0-100%;
+
+    public Pack(int id, String name, String description) {
+        super(id, name, description);
+    }
+
+    public void setProgression(List<Sticker> packStickers, List<Sticker> userStickers){
+        /* Takes in a list with all stickers in the pack and a list with all userStickers from the pack
+        *  These lists are taken from database in the Controllers via SQL query*/
+        int totalAmount = packStickers.size();
+        int hasAmount = userStickers.size();
+        progression = (int) ((totalAmount/hasAmount) * 100);
+    }
+    @Override
+    public String getImgFolder() {
+        return "packs";
+    }
+}