nostr challenge step much more robust

src/errors.js

@@ -5,6 +5,13 @@ class ChallengedUsedError extends Error {
     }
 }
 
+class AlreadyUsedError extends Error {
+    constructor(message) {
+        super(message);
+        this.name = "AlreadyUsedError"
+    }
+}
+
 class InvalidSignatureError extends Error {
     constructor(message) {
         super(message);
@@ -27,8 +34,7 @@ class NotFoundError extends Error {
 }
 
 module.exports = {
-    ChallengedUsedError,
+    AlreadyUsedError,
     InvalidSignatureError,
-    AppInvitedUsedError,
     NotFoundError
 };