Add nonce support

lib/helpers/api_helper.dart

@@ -41,7 +41,14 @@ class ApiHelper {
 
     ref
         .read(AuthCodeController.provider.notifier)
-        .set(code, MatrixUser(userId: userId, matrixToken: accessToken));
+        .set(
+          code,
+          MatrixUser(
+            userId: userId,
+            matrixToken: accessToken,
+            nonce: data["nonce"],
+          ),
+        );
 
     final uri = Uri.parse(redirectUri);
 
@@ -108,6 +115,7 @@ class ApiHelper {
             1000,
         "email": "$name@federated.nexus",
         "name": name,
+        "nonce": user.nonce,
         "iat": DateTime.now().millisecondsSinceEpoch ~/ 1000,
       },
       subject: user.userId,