use {"tag": ext} for extension-related payments.

lnbits/extensions/withdraw/models.py

@@ -62,5 +62,5 @@ class WithdrawLink(NamedTuple):
             k1=self.k1,
             min_withdrawable=self.min_withdrawable * 1000,
             max_withdrawable=self.max_withdrawable * 1000,
-            default_description="#withdraw LNbits LNURL",
+            default_description="LNbits voucher",
         )

lnbits/extensions/withdraw/views_api.py

@@ -182,7 +182,12 @@ def api_lnurl_callback(unique_hash):
         return jsonify({"status": "ERROR", "reason": f"Wait {link.open_time - now} seconds."}), HTTPStatus.OK
 
     try:
-        pay_invoice(wallet_id=link.wallet, payment_request=payment_request, max_sat=link.max_withdrawable)
+        pay_invoice(
+            wallet_id=link.wallet,
+            payment_request=payment_request,
+            max_sat=link.max_withdrawable,
+            extra={"tag": "withdraw"},
+        )
 
         changes = {
             "open_time": link.wait_time + now,