private static CacheItem CreateCacheItem(
            PersistedGrant entity)
        {
            CacheItem item = new CacheItem(entity);

            item.Tags = GetTags(entity);

            if (entity.GetExpiration().HasValue)
            {
                TimeSpan span = entity.GetExpiration().Value - DateTime.UtcNow;
                item.Expiration = new Expiration(ExpirationType.Absolute, span);
            }

            return(item);
        }