Force cache-control header

## 💬 Questions and Help

The file I'm try to cache does not provide a cache-control header. Is it possible to force this using fileService on a CustomCacheManager?

Start by tracing the fileService and CustomCacheManager APIs mentioned in the issue. Determine whether forcing a cache-control header is intended to be configurable there; done should include a documented behavior and a test, but the issue does not name specific files or tests.

索引モデルが issue の本文から書いたものです。