Use crypto.randomBytes for unique CLN invoice label (#1074)

lib/cln.js

@@ -1,10 +1,10 @@
 import fetch from 'node-fetch'
 import https from 'https'
+import crypto from 'crypto'
 
 export const createInvoice = async ({ socket, rune, cert, label, description, msats, expiry }) => {
   const agent = cert ? new https.Agent({ ca: Buffer.from(cert, 'base64') }) : undefined
   const url = 'https://' + socket + '/v1/invoice'
-  const randomId = Math.floor(Math.random() * 1000)
   const res = await fetch(url, {
     method: 'POST',
     headers: {
@@ -16,8 +16,9 @@ export const createInvoice = async ({ socket, rune, cert, label, description, ms
     },
     agent,
     body: JSON.stringify({
-      // why does CLN require a unique label?
-      label: description ? `${description} ${randomId}` : randomId,
+      // CLN requires a unique label for every invoice
+      // see https://docs.corelightning.org/reference/lightning-invoice
+      label: crypto.randomBytes(16).toString('hex'),
       description,
       amount_msat: msats,
       expiry