Sitemap data is cached forever with no option to clear it

[tomaszmadeyski]

With the following values in the configuration:

services.AddSitemaps(x =>
{
      x.EnableLanguageDropDownInAdmin = true;
      x.EnableRealtimeCaching = true;
      x.EnableRealtimeSitemap = true;
});

sitemap data is being cached forever due to the fact that the CacheEvictionPolicy is set to null (if I'm not a googleBot):

https://github.com/Geta/geta-optimizely-sitemaps/blob/master/src/Geta.Optimizely.Sitemaps/Controllers/GetaSitemapController.cs#L109

var cachePolicy = isGoogleBot
            ? new CacheEvictionPolicy(TimeSpan.Zero,
                                      CacheTimeoutType.Sliding,
                                      new[] { _contentCacheKeyCreator.VersionKey })
            : null;
CacheManager.Insert(cacheKey, sitemapData.Data, cachePolicy);

I think it would be reasonable to cache it for some limited period - maybe 1 day or maybe 1 day by default with an option to overwrite this value in configuration?