Add migration package for gating runnables behind pre-start migrations

[afritzler]

Proposed Changes

Add migration package for gating runnables behind pre-start migrations.

Summary by CodeRabbit

• New Features

  • Added migration support that runs registered migrations before application components start.
  • Migrations run concurrently, with completion and errors reported through the migration lifecycle.
  • Application components are prevented from starting if a migration fails.
  • Components exit cleanly when startup is canceled.

• Tests

  • Added coverage for migration execution, concurrency, failures, lifecycle behavior, and startup gating.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 55539517-48af-4c31-805f-f4fabaf9f141

📥 Commits

Reviewing files that changed from the base of the PR and between b20b6b1 and 6506cc0.

📒 Files selected for processing (2)

• migration/migration.go
• migration/migration_test.go

Included review availability: Your plan provides up to 1 included review per hour; 0 remain after this review.

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📝 Walkthrough

Walkthrough

Changes

Migration gating

Layer / File(s)	Summary
Migrator lifecycle migration/migration.go, migration/migration_test.go	Adds migration registration, concurrent execution, completion signaling, error aggregation, lifecycle validation, and tests for these behaviors.
Manager runnable gating migration/migration.go, migration/migration_test.go	Adds WrapManager, which delays runnable startup until migrations finish and handles migration errors and context cancellation. Tests cover each outcome.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: 🟡 Moderate · up to 6506c

This change gates manager runnables on concurrent startup migrations, but cancellation, partial migration failure, and startup ordering are not fully defined. A canceled migration could block services indefinitely or allow startup after incomplete work, while concurrent failures could leave partial state; these issues should be explicitly addressed or accepted before merging.

Suggested reviewers: adracus

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 40.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 5 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely identifies the new migration package and its purpose of gating runnables behind pre-start migrations.
Description check	✅ Passed	The description clearly states the main proposed change. It omits the template's Fixes # section and two placeholder entries, but the core change is sufficiently documented.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

• Fix all pre-merge checks with AI

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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