fix: [#726] scope log handler cache to the application

[krishankumar01]

📑 Description

RelatedTo goravel/goravel#726

The log module caches channel handlers in a package level sync.Map, so they survive facades.App().Restart(). Handlers that hold per container resources keep using the old ones after the restart; for the otel channel this means emitting into a shut down logger provider, which silently drops every record.

Scope the cache to the Application instead: instances derived via WithContext/Channel/Stack share it, and it dies with the container. Also removes the clearChannelCache() test helper that existed to work around the global.

@coderabbitai summary

✅ Checks

• Added test cases for my code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.40%. Comparing base (9e0d1e9) to head (885b2ae).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1482      +/-   ##
==========================================
- Coverage   69.40%   69.40%   -0.01%     
==========================================
  Files         377      378       +1     
  Lines       30190    30199       +9     
==========================================
+ Hits        20954    20959       +5     
- Misses       8256     8258       +2     
- Partials      980      982       +2     

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[Copilot]

Pull request overview

This PR fixes an application-restart correctness issue in the logging subsystem by scoping the log channel handler cache to a log.Application instance, rather than using a package-level global cache that could outlive the container and retain stale telemetry resources.

Changes:

• Replaced the package-level handler cache with an Application-scoped handlerCache shared across WithContext/Channel/Stack derived instances.
• Updated getHandlers to take an explicit cache parameter and thread it through stack recursion.
• Removed the prior global-cache test helper and added a test ensuring cache sharing/leakage behavior matches the new scoping.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
log/application.go	Introduces per-Application handler cache and ensures derived instances share it while new root apps don’t.
log/application_test.go	Removes global cache helper; adds coverage verifying cache scope and updates getHandlers call sites.
log/writer_test.go	Removes now-unneeded cache clearing calls that were compensating for the prior global cache.

[hwbrzzl]

Is a pointer required?

Suggested change

	handlerCache *sync.Map
	channelToHandlers sync.Map

[krishankumar01]

It is required, we want an application level cache here. Channel/WithContext/Stack create a new Application each call and all of them should share the same cache. If we make it a value, each instance gets a copy of the map, so if someone calls Channel multiple times it will create the handlers each time since whatever was cached stays in the copy. Also vet doesn't allow copying sync.Map by value, it has a mutex inside.

[krishankumar01]

But I have renamed handlerCache -> channelToHandlers

[hwbrzzl]

Thanks, LGTM