feat: add catalog search, ordering, and trigram indexes

[TenSt]

📜 Checklist

• Commits are cleanly separated with meaningful messages (simple features and bug fixes should be squashed to one commit)
• A changelog entry or entries has been added for any significant changes
• [x Follows the Pulp policy on AI Usage
• (For new features) - User documentation and test coverage has been added

Summary

This PR:

• Adds search on repository packages/ (contains on groupId/artifactId; group:artifact ANDs both)
• Adds last_updated and ordering so clients can sort the catalog
• Lists versions newest-first using numeric version order
• Adds pg_trgm GIN indexes on group_id and artifact_id for ILIKE filters
• Treats a trailing .letters-... last-segment suffix as a rebuild qualifier, so 5.3.17.rhlw-00001 and 5.3.17.rhlw-00001-n0001 share base version 5.3.17

Closes #450
Closes #459

[dkliban]

Review

1. Migration will block writes (needs fix)

migrations.AddIndex takes an ACCESS EXCLUSIVE lock — blocking all reads and writes on core_mavenpackage while the index builds. Use AddIndexConcurrently instead (the same pattern used in pulpcore's 0147_content_pulp_labels_gin.py):

from django.contrib.postgres.operations import AddIndexConcurrently, TrigramExtension

class Migration(migrations.Migration):
    atomic = False  # required for CONCURRENTLY

    operations = [
        TrigramExtension(),
        AddIndexConcurrently(
            model_name="mavenpackage",
            index=GinIndex(fields=["group_id"], name="maven_pkg_group_id_trgm", opclasses=["gin_trgm_ops"]),
        ),
        AddIndexConcurrently(
            model_name="mavenpackage",
            index=GinIndex(fields=["artifact_id"], name="maven_pkg_artifact_id_trgm", opclasses=["gin_trgm_ops"]),
        ),
    ]

Note: atomic = False means no automatic rollback — a failed AddIndexConcurrently may leave an invalid index requiring manual DROP INDEX CONCURRENTLY IF EXISTS before re-running.

pg_trgm is a trusted extension on RDS PostgreSQL 13+ so TrigramExtension() will work fine with the application DB user — no DBA intervention needed.

2. Lint failure in CI

ruff reports I001 (unsorted imports) in pulp_maven/app/migrations/0010_mavenpackage.py:3 — pulpcore.app.util must move after the django imports. Fix with:

ruff check --fix pulp_maven/app/migrations/0010_mavenpackage.py

[dkliban]

Correction to my earlier review: I was wrong about TrigramExtension() requiring superuser on RDS. According to AWS docs, pg_trgm is a trusted extension on PostgreSQL 13+ — any user with CREATE privilege on the database can install it, no rds_superuser needed. The TrigramExtension() call in the migration is fine as-is.

The two remaining concerns stand: blocking index creation (use AddIndexConcurrently) and the lint failure.