ISR does not seem to work #398

Brief Description of the Bug
When using the App directory, calling revalidateTag will delete all entries with the specified tag. When the user browses a page that was tagged with the tag, the page is rebuilt during the request, causing a delay for the user. I would have expected the page to be rebuilt in the background after the request has been served, as happens when using the built-in CacheHandler.

Severity
Major

Frequency of Occurrence
Always

Steps to Reproduce

1. Navigate to a page '/test' with tag 'xyz'
2. call revalidateTag('xyz') in an api endpoint - this deletes the cache entries for the tag
3. Browse to '/test' - the page is rebuilt inline rather than in the background

Expected vs. Actual Behavior
I would expect the page to be rebuilt in the background and the user who initiated the request to be served the stale content.

Environment:

• OS: MacOS
• Node.js version: v20.10.0
• @neshca/cache-handler version: 1.0.5
• next version: 14.1.0

Attempted Solutions or Workarounds

• Looked into how the stock CacheHandler works - it seems that we would need to replicate the behaviour in FetchCache and FileSystemCache?
• Referenced https://github.com/sst/open-next/blob/ff37de235e653e3aecdbb31168ab411add2d0330/packages/open-next/src/adapters/cache.ts#L81 - but it's unclear whether the approach used there would improve the situation - as they appear to use a custom revalidation system.

Impact of the Bug
We would like to containerize our app, building on a remote CI environment using a shared cache, and have ready-to-run testable Containers as built output - and this is a blocker for us