feat: add external nullifier as optional parameter

package.json

@@ -1,6 +1,6 @@
 {
     "name": "zuauth",
-    "version": "0.3.0",
+    "version": "0.4.0",
     "license": "GPL-3.0-or-later",
     "main": "./dist/index.js",
     "types": "./dist/index.d.ts",

src/utils.ts

@@ -16,6 +16,7 @@ import { openZupassPopup } from "./passport-interface/PassportPopup"
 export function openZKEdDSAEventTicketPopup(
     fieldsToReveal: EdDSATicketFieldsToReveal,
     watermark: string | bigint,
+    externalNullifier?: string | bigint,
     validEventIds: string[] = supportedEvents,
     validProductIds: string[] = supportedProducs,
     popupRoute: string = "popup"
@@ -55,7 +56,7 @@ export function openZKEdDSAEventTicketPopup(
         },
         externalNullifier: {
             argumentType: ArgumentTypeName.BigInt,
-            value: watermark.toString(),
+            value: externalNullifier ? externalNullifier.toString() : watermark.toString(),
             userProvided: false
         }
     }