Saving CalendarListEntry in Firestore on Flutter

Saving a CalendarListEntry object in Firestore on Flutter used to work. But after upgrading my Googleapis to v7.0.0, it started to raise Invalid argument: Instance of 'ConferenceProperties' error. I think this is because of this commit.

How can I save a CalendarListEntry object in Firestore on Flutter?

I have used Freezed. My model looks like this.

@freezed
class GoogleCalendarProject with _$GoogleCalendarProject {
  const factory GoogleCalendarProject({
    required CalendarListEntry calendar,
    @DocumentReferenceNullableConverter() DocumentReference? projectRef,
  }) = _GoogleCalendarProject;
  factory GoogleCalendarProject.fromJson(Map<String, dynamic> json) =>
      _$GoogleCalendarProjectFromJson(json);
}