TF-1115 Add CacheExceptionThrower

lib/main/exceptions/cache_exception.dart

@@ -0,0 +1,16 @@
+
+import 'package:equatable/equatable.dart';
+
+abstract class CacheException with EquatableMixin implements Exception {
+
+  final String? message;
+
+  const CacheException({this.message});
+}
+
+class UnknownCacheError extends CacheException {
+  const UnknownCacheError({String? message}) : super(message: message);
+
+  @override
+  List<Object> get props => [];
+}