Migrate runtime service registry metadata

[josecelano]

Goal

Migrate Registar registrations to carry canonical tracker service role, configuration-instance identity, and final listener binding metadata. Make this metadata queryable without running a health check or depending on bind-IP conventions.

Background

Issue #2036 now owns canonical tracker identity types only. This issue owns the dependent migration of torrust-server-lib registration metadata and tracker registrations after #2035 propagates that identity through actual bootstrap.

This migration is required before #2039 can use canonical runtime identity for event-metrics policy filtering. It also replaces #1419's temporary bind-IP classification and fixed registration delay.

Scope

• Extend torrust-server-lib::ServiceRegistration with generic immutable metadata and optional health behavior.
• Publish and upgrade a compatible torrust-server-lib release.
• Carry canonical role and configuration-instance identity into all tracker service registrations.
• Provide deterministic, side-effect-free registry queries and registration readiness.
• Preserve health-check response compatibility.
• Replace Allow multiple integration tests at the main app level #1419 bind-IP classification and fixed startup delay.

Prerequisites

• Define canonical runtime service identity #2036 canonical service role and configuration-instance identity types.
• Fix duplicate port-zero tracker instance bootstrap #2035 bootstrap propagation of canonical identity.

Implementation outline

1. Define generic registration metadata boundary.
2. Extend registration/query/readiness API.
3. Release and upgrade standalone server library.
4. Migrate tracker registrations and health reporting.
5. Replace Allow multiple integration tests at the main app level #1419 endpoint discovery helpers.
6. Add tests and progressive manual baseline/post-change evidence.

Acceptance criteria

• Registrations expose final binding and opaque metadata without network health checks.
• Tracker registrations carry canonical role and configuration-instance identity.
• Registry queries are deterministic and readiness is testable.
• Health-check JSON stays compatible.
• Allow multiple integration tests at the main app level #1419 discovers endpoints by role/identity without bind-IP conventions or fixed delay.
• Port-zero/repeated configuration blocks retain identity.
• Both repository validation suites and manual verification pass.

Related to #1419, #2035, #2036, and #2039.

See docs/issues/drafts/migrate-runtime-service-registry-metadata/ISSUE.md until the specification PR merges.