TF-1008 Create the SetError Handler

model/lib/error_type_handler/set_method_error_handler_mixin.dart

@@ -0,0 +1,7 @@
+import 'package:jmap_dart_client/jmap/core/error/set_error.dart';
+import 'package:jmap_dart_client/jmap/core/id.dart';
+
+typedef SetMethodErrors = Map<Id, SetError>;
+
+/// Returns true if handle [setError] successfully and otherwise
+typedef SetMethodErrorHandler = bool Function(MapEntry<Id, SetError> setError);