feat: add persistent inventory storage slots

tests/inventory_storage_persistence_validation.gd

@@ -0,0 +1,67 @@
+extends SceneTree
+
+const MainScene: PackedScene = preload("res://main/main.tscn")
+
+
+func _initialize() -> void:
+	call_deferred("_run")
+
+
+func _run() -> void:
+	root.size = Vector2i(1280, 720)
+	var main: Node = MainScene.instantiate()
+	root.add_child(main)
+	for _frame: int in 4:
+		await process_frame
+	if not bool(main.get("_application_initialized")):
+		main.call("_activate_selected_data_path", "", true)
+	for _frame: int in 8:
+		await process_frame
+	assert(bool(main.get("_application_initialized")))
+
+	var save_manager := main.get("_save_manager") as PlayerSaveManager
+	var player := main.get("_player") as Player
+	assert(save_manager != null and player != null)
+	assert(save_manager.initialize_new_game())
+	save_manager.set_autosave_enabled(true)
+	assert(player.bag.add_item(&"art_kit"))
+	assert(player.bag.add_item(&"coffee"))
+	assert(player.bag.move_item_to_storage_slot(&"basic_fishing_rod", 14))
+	assert(player.bag.move_item_to_storage_slot(&"coffee", 12))
+	assert(save_manager.save_now())
+
+	var save_file := FileAccess.open(
+		str(save_manager.get("_save_path")),
+		FileAccess.READ,
+	)
+	assert(save_file != null)
+	var parsed: Variant = JSON.parse_string(save_file.get_as_text())
+	save_file.close()
+	assert(typeof(parsed) == TYPE_DICTIONARY)
+	var records: Array = (parsed as Dictionary)["bag"]["items"]
+	assert(_saved_slot(records, &"basic_fishing_rod") == 14)
+	assert(_saved_slot(records, &"coffee") == 12)
+
+	assert(player.bag.move_item_to_storage_slot(&"basic_fishing_rod", 0))
+	assert(player.bag.move_item_to_storage_slot(&"coffee", 0))
+	assert(save_manager.load_player_data())
+	assert(player.bag.get_storage_slot(&"basic_fishing_rod") == 14)
+	assert(player.bag.get_storage_slot(&"coffee") == 12)
+
+	main.queue_free()
+	for _frame: int in 4:
+		await process_frame
+	await create_timer(0.1).timeout
+	print("Inventory storage persistence validation: PASS")
+	quit()
+
+
+func _saved_slot(records: Array, item_id: StringName) -> int:
+	for value: Variant in records:
+		if (
+			typeof(value) == TYPE_DICTIONARY
+			and str((value as Dictionary).get("item_id", ""))
+			== String(item_id)
+		):
+			return int((value as Dictionary).get("storage_slot", -1))
+	return -1