fix: avoid stale autoload misses during upgrades

[vitormattos]

Summary

• add regression coverage for same-process upgrade-time autoload misses cached by Composer
• rebuild the current LibreSign Composer loader from Composer-generated metadata before migrations run
• register the refresh as a pre-migration repair step so newly introduced migrations and their fresh dependencies stay loadable during the same upgrade request
• rename the repair step to RefreshAutoloaderBeforeMigrations so the name matches the behavior

Fixes #7892.

Testing

• composer test:unit -- --filter "UpgradeSafeAutoloaderTest|RefreshAutoloaderBeforeMigrationsTest"
• composer cs:check

[vitormattos]

/backport to stable34

[vitormattos]

/backport to stable33

[vitormattos]

/backport to stable32

[Copilot]

Pull request overview

This PR addresses upgrade-time autoload failures where Composer can cache previous “class not found” misses within the same PHP process, causing newly introduced migration classes to be reported as “unknown” during upgrades. It introduces an app-level mitigation by rebuilding and re-registering LibreSign’s Composer loader immediately before migrations run, plus regression tests for the scenario.

Changes:

• Add UpgradeSafeAutoloader to rebuild the app’s Composer\Autoload\ClassLoader from Composer-generated metadata and reload Composer “files” autoloaders.
• Register a new pre-migration repair step RefreshAutoloaderBeforeMigrations in appinfo/info.xml to refresh the loader just before migrations execute.
• Add unit tests to cover autoload refresh behavior and same-process upgrade-time autoload miss caching.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tests/php/Unit/Migration/UpgradeSafeAutoloaderTest.php	Adds regression tests simulating same-process autoload miss caching and validating loader refresh behavior.
tests/php/Unit/Migration/RefreshAutoloaderBeforeMigrationsTest.php	Adds unit test coverage for the new pre-migration repair step refreshing the current app loader.
lib/Migration/UpgradeSafeAutoloader.php	Implements rebuilding/re-registering a fresh ClassLoader from Composer metadata and re-loading autoload “files”.
lib/Migration/RefreshAutoloaderBeforeMigrations.php	Adds a pre-migration repair step that refreshes LibreSign’s autoloader before Nextcloud migrations run.
appinfo/info.xml	Registers the new repair step under <pre-migration> to ensure it runs before migrations.