refactor: dev-friendly payment status name (#2322)

* refactor: dev-friendly payment status name
* refactor: change `PaymentStatus(True, ...)` to `PaymentSuccessStatus(...)`

lnbits/wallets/base.py

@@ -52,6 +52,18 @@ class PaymentStatus(NamedTuple):
             return "unknown (should never happen)"
 
 
+class PaymentSuccessStatus(PaymentStatus):
+    paid = True
+
+
+class PaymentFailedStatus(PaymentStatus):
+    paid = False
+
+
+class PaymentPendingStatus(PaymentStatus):
+    paid = None
+
+
 class Wallet(ABC):
     async def cleanup(self):
         pass