TF-106 Fix display inlined image CIDs of emails

core/lib/data/extensions/options_extensions.dart

@@ -0,0 +1,12 @@
+import 'package:dio/dio.dart';
+
+extension OptionsExtension on Options {
+  Options appendHeaders(Map<String, dynamic> additionalHeaders) {
+    if (this.headers != null) {
+      this.headers?.addAll(additionalHeaders);
+    } else {
+      this.headers = additionalHeaders;
+    }
+    return this;
+  }
+}