Enhance documentation

src/app/markets/coinbase.py

@@ -2,6 +2,10 @@ from coinbase.rest import RESTClient
 from app.markets.base import ProductInfo, BaseWrapper, Price
 
 class CoinBaseWrapper(BaseWrapper):
+    """
+    Wrapper per le API di Coinbase.
+    La documentazione delle API è disponibile qui: https://docs.cdp.coinbase.com/api-reference/advanced-trade-api/rest-api/introduction
+    """
     def __init__(self, api_key:str, api_private_key:str, currency: str = "USD"):
         assert api_key is not None, "API key is required"
         assert api_private_key is not None, "API private key is required"