feat: add Breez *Liquid* SDK funding source (#2681)

Co-authored-by: Pavol Rusnak <pavol@rusnak.io>
Co-authored-by: dni ⚡ <office@dnilabs.com>
Co-authored-by: Vlad Stan <stan.v.vlad@gmail.com>

lnbits/core/crud/payments.py

@@ -268,7 +268,7 @@ async def create_payment(
         preimage=data.preimage,
         expiry=data.expiry,
         webhook=data.webhook,
-        fee=data.fee,
+        fee=-abs(data.fee),
         tag=extra.get("tag", None),
         extra=extra,
     )