FirebaseCacheManager uses DownloadUrl which has a token in the url defeating cache

[FirebaseCacheManager](https://github.com/Baseflow/flutter_cache_manager/blob/develop/flutter_cache_manager_firebase/lib/src/firebase_http_file_service.dart#L36) uses the `ref.getDownloadUrl()` which typically returns a url with a dynamic access token in the query string of the URL. Doesn't that mostly defeat the purpose of the cache, assuming that the key of the file in the cache is tho whole url including the token?

从 flutter_cache_manager_firebase/lib/src/firebase_http_file_service.dart 中引用的那一行开始，然后跟踪下载 URL 如何变成缓存键。检查更改 Firebase 访问令牌是否会创建单独的缓存条目；当缓存行为得到验证，并且报告的问题已通过涵盖相关情况得到解决时，即视为完成。

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