feat: allow extra appending (#3974)

Co-authored-by: Arc <ben@arc.wales>

lnbits/core/views/payment_api.py

@@ -34,6 +34,7 @@ from lnbits.core.models import (
     PaymentWalletStats,
     SettleInvoice,
     SimpleStatus,
+    UpdatePaymentExtra,
 )
 from lnbits.core.models.payments import UpdatePaymentLabels
 from lnbits.core.models.users import AccountId
@@ -297,6 +298,38 @@ async def api_update_payment_labels(
     return SimpleStatus(success=True, message="Payment labels updated.")
 
 
+@payment_router.patch(
+    "/extra",
+    name="Update payment extra",
+    description="Append new extra metadata to a payment.",
+    response_model=Payment,
+)
+async def api_update_payment_extra(
+    data: UpdatePaymentExtra,
+    key_type: WalletTypeInfo = Depends(require_admin_key),
+) -> Payment:
+    payment = await get_standalone_payment(
+        data.payment_hash, wallet_id=key_type.wallet.id
+    )
+    if payment is None:
+        raise HTTPException(HTTPStatus.NOT_FOUND, "Payment does not exist.")
+    if not payment.success:
+        raise HTTPException(
+            HTTPStatus.BAD_REQUEST, "Payment extra can only be updated after success."
+        )
+
+    duplicate_keys = sorted(set(payment.extra).intersection(data.extra))
+    if duplicate_keys:
+        raise HTTPException(
+            HTTPStatus.BAD_REQUEST,
+            f"Extra keys already exist: {', '.join(duplicate_keys)}.",
+        )
+
+    payment.extra.update(data.extra)
+    await update_payment(payment)
+    return payment
+
+
 @payment_router.get("/fee-reserve")
 async def api_payments_fee_reserve(invoice: str = Query("invoice")) -> JSONResponse:
     invoice_obj = bolt11.decode(invoice)