feat(BA-6704): cascade app config subtree deletion from the definition

[jopemachine]

Summary

Ties fragments to their allow-list entry with a composite FK and lets deletion cascade the whole subtree definition → allow_list → fragment (BEP-1052 review feedback):

• Composite FK with ON DELETE CASCADE. app_config_fragments (config_name, scope_type) references app_config_allow_list, so purging an allow-list entry drops every fragment written under it — a revoked value disappears from the merge in the same statement, with no orphaned fragments to clean up separately.
• Cascade from the definition, with exactly two FKs. app_config_allow_list.config_name → app_config_definitions changes from NO ACTION to ON DELETE CASCADE, and the redundant direct app_config_fragments.config_name → app_config_definitions FK is dropped (not made cascade). A fragment already requires a matching allow-list entry (composite FK, both columns NOT NULL) whose config_name is registered, so registration is guaranteed transitively — the direct FK added no integrity and only blocked the definition delete (a NO ACTION check firing before the allow-list cascade cleared the fragments). Result: retiring a config name (DELETE its definition row) cascades cleanly through allow_list down to the fragments.
• Write-gate cleanup. With the composite FK in place, a fragment row can only exist while its allow-list entry does, so the only_if gates on fragment update/purge are provably dead and are removed (from the actions, service, repository, and db_source). The create gate stays — it surfaces the domain error (AppConfigFragmentWriteNotAllowed) instead of a raw FK violation.
• Single migration a560420476b6: deletes orphaned fragments, adds the composite allow-list FK, swaps the allow-list→definition FK to CASCADE, and drops the redundant direct fragment→definition FK. Constraint names are discovered via the inspector (they differ between a migration-built DB and a metadata-built dev DB). Upgrade/downgrade round-trip and the live definition → allow_list → fragment cascade were verified against a local DB; the end state is exactly two FKs.
• BEP-1052 updated: cascade semantics on allow-list purge and on definition retirement, the transitive-registration model (fragments need no direct definition FK), the corrected read model (the merge must join the allow-list for rank — the "reads never consult the allow-list" wording was stale), and the create-only write gate.

📚 Stacked PRs

Part of the AppConfigFragment / AppConfig stack under BEP-1052 (epic BA-5781). Merge in order:

1. ✅ feat(BA-6552): add app_config_fragments DB model and Alembic migration #12306 — feat(BA-6552): app_config_fragments DB model and Alembic migration
2. ✅ feat(BA-6553): add app_config_fragments repository layer #12307 — feat(BA-6553): repository layer
3. ✅ refactor(BA-6619): consolidate AppConfigScopeType into common.data (single definition) #12403 — refactor(BA-6619): consolidate AppConfigScopeType into common.data
4. ✅ refactor(BA-6620): ExistsQuerier ops primitive + AppConfigAllowList.exists #12405 — refactor(BA-6620): ExistsQuerier + AppConfigAllowList.exists
5. ✅ feat(BA-6554): add app_config_fragment service layer #12358 — feat(BA-6554): AppConfigFragment service layer
6. feat(BA-6702): move fragment rank to the allow list with scope defaults #12516 — feat(BA-6628): move fragment rank to the allow list with scope defaults (replaces feat(BA-6628): conditional-bulk repository primitives #12429)
7. feat(BA-6701): expose allow-list rank on the v2 API surface #12517 — feat(BA-6628): expose allow-list rank on the v2 API surface
8. 👉 feat(BA-6704): cascade app config subtree deletion from the definition #12518 — feat(BA-6704): cascade app config subtree deletion from the definition ← you are here
9. feat(BA-6626): app_config_fragment bulk repository layer #12426 — feat(BA-6626): app_config_fragment bulk repository layer
10. feat(BA-6618): app_config_fragment bulk CRUD service layer #12401 — feat(BA-6618): AppConfigFragment bulk CRUD service layer
11. feat(BA-6555): AppConfig merge engine + resolve service (service layer) #12359 — feat(BA-6555): app_config service layer (merge engine)
12. feat(BA-6556): AppConfig REST v2 API (raw fragments and merged read/update) #12377 — feat(BA-6556): AppConfig REST v2 API

🤖 Generated with Claude Code

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📚 Documentation preview 📚: https://sorna--12518.org.readthedocs.build/en/12518/

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📚 Documentation preview 📚: https://sorna-ko--12518.org.readthedocs.build/ko/12518/

[Copilot]

Pull request overview

Copilot reviewed 27 out of 27 changed files in this pull request and generated 1 comment.