IBX-12606: Replaced the Symfony deprecation thresholds with PHPUnit's native deprecation gate

[ViniTou]

🎫 Issue	IBX-12606

Description:

SYMFONY_DEPRECATIONS_HELPER thresholds are dead under PHPUnit >=10: phpunit-bridge no longer registers a DeprecationErrorHandler, so trigger_deprecation() calls were silently ignored. This replaces it with PHPUnit 11's native gate: failOnDeprecation + a per-config <source baseline="..."> scoped to src/lib, src/contracts and src/bundle, so CI fails only on NEW deprecations.

phpunit.xml and phpunit-integration.xml are gated. phpunit.xml's baseline carries 2 issues (both League\Flysystem\Local\LocalFilesystemAdapter::__construct() implicit-nullable-parameter deprecations, PHP 8.4-only); phpunit-integration.xml's baseline is empty: 0 issues — no pre-existing src-level deprecations. phpunit-integration-legacy.xml and phpunit-integration-legacy-solr.xml are left ungated: neither had a SYMFONY_DEPRECATIONS_HELPER line to remove. The legacy suite now passes locally (exit 0; the non-static data-provider issue was fixed by #352). The solr suite still needs a running Solr instance on localhost:8983 that isn't available locally, so it remains unverified here. Gating those two is left for CI/a follow-up.

Verified with a trigger_deprecation() probe in src/lib/FieldType/RichText/Value.php (constructor, exercised by hundreds of unit tests): the unit suite correctly failed, then passed again after removal (git diff -- src clean). composer check-cs and phpstan analyse are unchanged (clean).

To refresh a baseline: ensure vendor/ is a real (non-symlinked) directory with PHPUnit 11 installed, then run vendor/bin/phpunit -c <config> --generate-baseline <baseline>.

Base branch: 6.0 (the PHPUnit 11 migration landed as ec4f4e3 — squash-merge of #352 — and this branch is now rebased directly onto it).

• ignoreIndirectDeprecations is deliberately false: PHPUnit classifies a Symfony deprecation caused by our code as "indirect" (callee deprecation-contracts/function.php, caller the vendor method), so true would silently drop every deprecated-vendor-API usage. Vendor-originated baseline entries are expected; new ones fail the build until the baseline is refreshed on purpose.
• Baselines were generated on the repo's highest CI PHP version at the time of authoring; regenerate with whatever is currently the highest version in the matrix (currently 8.3 — this repo's CI matrix has since dropped 8.4).

Re-verified after the rebase onto 6.0: failOnWarning="true" failOnNotice="true" are already present on every phpunit*.xml config (added by #352), symfony/phpunit-bridge is already fully gone from composer.json with zero remaining usages anywhere in the repo, and no ExpectDeprecationTrait/expectDeprecation() calls exist to convert. No additional commits were needed on top of the deprecation-gate commit. Both gated suites (phpunit.xml, phpunit-integration.xml) still pass with the existing baselines on PHP 8.3 (exit 0); phpunit-integration-legacy-solr.xml is unrunnable locally (needs a live Solr instance on localhost:8983) but is unaffected by this change since it isn't gated.

For QA:

N/A

Documentation:

N/A

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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