Revert "Rename everything filcnaplo-related to refilc"

This reverts commit d1a9625d93.

filcnaplo/lib/api/nonce.dart

@@ -0,0 +1,25 @@
+import 'dart:convert';
+import 'package:crypto/crypto.dart';
+
+class Nonce {
+  String nonce;
+  List<int> key;
+  String? encoded;
+
+  Nonce({required this.nonce, required this.key});
+
+  Future encode(String message) async {
+    List<int> messageBytes = utf8.encode(message);
+    Hmac hmac = Hmac(sha512, key);
+    Digest digest = hmac.convert(messageBytes);
+    encoded = base64.encode(digest.bytes);
+  }
+
+  Map<String, String> header() {
+    return {
+      "X-Authorizationpolicy-Nonce": nonce,
+      "X-Authorizationpolicy-Key": encoded ?? "",
+      "X-Authorizationpolicy-Version": "v2",
+    };
+  }
+}