Add the methods to show cart items and to add an item to a cart.

src/api/v2/cart_api.py

@@ -0,0 +1,58 @@
+import aiohttp
+import asyncio
+import ujson
+
+class CartAPI:
+    def __init__(self, fetcher, formatter):
+        """
+        Sets needed classes:
+
+        Fetcher (ApiFetcher) - class that will fetch data.
+        Format  (AbstractFormat) - class that will format response data.
+        """
+        self.__fetcher, self.__formatter = fetcher, formatter
+
+    async def get_dict(self, username: str):
+        endpoint = f"/api/v2/cart?matrixUsername={username}"
+
+        status, json_data = await self.__fetcher.fetch_json(endpoint)
+
+        if status == 200:
+            return {"ok": json_data}
+
+        return {"error": "Сталася помилка, спробуйте пізніше."}
+
+    async def add_obj(self, item_name: str, count: int, username: str):
+        endpoint = "/api/v2/add-item"
+
+        status, json_data = await self.__fetcher.send_json(endpoint, {
+            'itemName': item_name,
+            'itemCount': count,
+            'matrixUsername': username,
+        })
+
+        if status == 200:
+            return {"ok": json_data}
+
+        return {"error": "Сталася помилка, спробуйте пізніше."}
+
+    async def get_objects_message(self, username: str) -> str:
+        response = await self.get_dict(username)
+
+        match response:
+            case {"ok": json_data}:
+                return self.__formatter.format_all(json_data)
+
+            case {"error": error_message}:
+                return error_message
+
+    async def add_object_message(self, item_name: str, count: int, username: str) -> str:
+        response = await self.add_obj(item_name, count, username)
+
+        match response:
+            case {"ok": json_data}:
+                return 'Успішно додано'
+
+            case {"error": error_message}:
+                return error_message
+