Refactor serialization in ChestShopMetaData class

The serialization and deserialization methods in the ChestShopMetaData class have been modified. UUID fields are now saved and reloaded as strings rather than as UUID objects to ensure correct data persistence. Alongside, necessary changes were addressed during the transformation to and from a string to UUID.

src/main/java/com/Acrobot/ChestShop/Signs/ChestShopMetaData.java

@@ -88,8 +88,12 @@ public ItemStack getItemStack() {
     @Override
     public Map<String, Object> serialize() {
         Map<String, Object> data = new HashMap<>();
-        data.put("owner", owner);
-        data.put("accessors", accessors);
+        data.put("owner", owner.toString());
+
+        Set<String> accessorsStrings = new HashSet<>();
+        this.accessors.forEach(uuid -> accessorsStrings.add(uuid.toString()));
+        data.put("accessors", accessorsStrings);
+
         data.put("amount", quantity);
         data.put("buyPrice", buyPrice);
         data.put("sellPrice", sellPrice);
@@ -99,12 +103,16 @@ public Map<String, Object> serialize() {
 
     public static ChestShopMetaData deserialize(Map<String, Object> map) {
 
-        UUID owner = (UUID) map.get("owner");
+        UUID owner = UUID.fromString((String) map.get("owner"));
         int amount = (int) map.get("amount");
         double sellPrice = (double) map.get("sellPrice");
         double buyPrice = (double) map.get("buyPrice");
-        ItemStack itemStack = (ItemStack) map.get("itemStack");
-        Set<UUID> accessors = new HashSet<>((HashSet<UUID>) map.get("accessors"));
+        ItemStack itemStack = ItemStack.deserialize((Map<String, Object>) map.get("itemStack"));
+
+        Set<String> accessorsString = (HashSet<String>) map.get("accessors");
+        Set<UUID> accessors = new HashSet<>();
+        accessorsString.forEach(string -> accessors.add(UUID.fromString(string)));
+
         return new ChestShopMetaData(owner, amount, sellPrice, buyPrice, itemStack, accessors);
     }
 }