[Symfony 8] Add central Symfony 8 compatibility check

[herbertroth]

What

Adds .github/workflows/symfony8-compat.yaml — a thin caller for the central, reusable Symfony 8
compatibility check:

uses: pimcore/workflows-collection-public/.github/workflows/reusable-symfony8-compat.yaml@main

No source code is changed — this repo already has 0 usages of the APIs the check bans.

Why

Symfony 7.4 → 8 removes a number of APIs Pimcore uses. As each one is fixed across the platform, a rule is
added to the central check, and from then on every subscribed repo is guarded against it — no repo has
to maintain its own list, and a regression is caught on the PR that introduces it instead of during the
Symfony 8 bump.

Rules active today (both from Symfony 8.0, DependencyInjection):

id	bans
tagged-iterator-attribute	#[TaggedIterator( — use #[AutowireIterator]
tagged-iterator-import	use Symfony\Component\DependencyInjection\Attribute\TaggedIterator;

Each rule is its own named check and annotates the offending line, so a red PR says exactly what to fix.
Verified for this repo before opening: 0 matches for either rule.

Verification

The check runs on this PR itself, so a green symfony8-compat proves the wiring and the clean state in
one signal. The only file added is the workflow.

Context

Step 1 of the Symfony 7.4 → 8 migration, from the readiness analysis of all 37 platform SBOM repos
(pimcore/platform-version, migration-analysis/SUMMARY.md). The central workflow was added in
pimcore/workflows-collection-public#154; 9 repos additionally needed the #[TaggedIterator] rename, which
is happening in parallel PRs.

🤖 Generated with Claude Code

[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

See analysis details on SonarQube Cloud

[Copilot]

Pull request overview

Verdict: LGTM

Adds the repository-level caller for the central Symfony 8 compatibility workflow (.github/workflows/symfony8-compat.yaml:1-10).

Changes:

• Runs compatibility checks for pull requests and manual dispatches (:3-6).
• Delegates checks to the central reusable workflow (:8-10).

Review contract:

1. Claim: Adds centralized Symfony 8 regression detection.
2. Root cause: Addresses duplicated compatibility rules through central delegation (:10).
3. Call sites: Repository-wide workflow; no application call sites.
4. Boundary: Correctly implemented in GitHub Actions configuration.
5. Backward compatibility: No source or public API changes.
6. Regression test: The workflow execution is the relevant verification seam.
7. Docs/changelog: Not required for an internal CI addition.
8. Remaining risks: The intentional @main reference allows central behavior to evolve.

Findings: None.