feat: add authz schema applier

[rodmgwgu]

Problem

Rendered rows have to reach the database without damaging anything the schema loader does not own. The apply step shares tables with dynamic roles, user assignments and the legacy g2 action-inheritance rows, so it needs a change report before any write, precise ownership-scoped removal, and a single transaction (ADR 0018 §2, §3, §6, ADR 0025 §6).

Approach

The rest of openedx_authz/engine/renderer.py, on top of the render half in #479.

• SchemaApplier.plan() — the change report: p rows to add or remove, plus definition-level diffs including metadata-only edits that change no policy row at all
• SchemaApplier.apply() — one transaction: add missing rows, remove stale rows it owns, prune definition/source records the compiled schema no longer contains, invalidate the policy cache
• ChangePlan, DefinitionDiff, ApplyResult
• openedx_authz/tests/schema/{test_apply,test_source_storage}.py, openedx_authz/tests/integration/test_schema_apply.py

Three properties worth reviewing directly:

• Ownership is consulted, not assumed. Removal candidates are intersected with the stored role-permission grants, so unmanaged p rows, dynamic roles, user assignments and legacy g2 rows survive.
• Adoption, not duplication (ADR 0025 §6). A rendered row that already exists gains definition and source records without being rewritten, which is why applying to a database that already ran load_policies adds zero rows.
• Removal is force-gated (ADR 0018 §6). A role slated for removal that still has assignments aborts before any write; with force its rows and assignments go together and a RoleAssignmentAudit record is written per removed assignment.

Manual testing instructions

pytest openedx_authz/tests/

The integration module is excluded from the default pytest run and needs an edx-platform environment. It exercises the real Casbin enforcer and ORM, including enforce() assertions for permission removal, force-removal, adoption and failure rollback:

tutor dev run cms pytest -p no:randomly --create-db --ds=cms.envs.test \
    /mnt/openedx-authz/openedx_authz/tests/integration/test_schema_apply.py

End-to-end exercise through the management command is in 8/8, which is the only thing that calls the applier.

Rollback plan

Revert this PR. Nothing invokes the applier until the command lands in 8/8, so the revert is inert. If it has already run, the definition tables it populated are additive and the Casbin rows it wrote match what authz.policy already defines.

Retro compatibility

No authorization behavior changes. Loading authz.policy works as before, and no code path reaches the applier until the management command lands.

AI Usage

Kiro was used to assist on feature planning and implementation. Implementation was done step by step with human guidance and validation, based on the ADRs.

---

Stack (7/8) — #446 split into reviewable pieces. Bases chain bottom-up; merge in order.

1. feat: add authz schema discovery #474 — schema discovery
2. feat: add authz schema loading #475 — schema loading
3. feat: add authz schema compilation #476 — schema compilation
4. feat: add authz schema validation #477 — schema validation
5. feat: add authz schema definition models #478 — definition models + migration
6. feat: add authz schema policy renderer #479 — policy renderer
7. This PR — schema applier (base: rod/authz-schema-renderer)
8. feat: add authz schema pipeline and load_authz_schema command #446 — pipeline + load_authz_schema command, version bump and changelog

Largest PR in the stack. It is the one part that cannot be subdivided without landing apply() calling methods added in a later PR.

Merge checklist:

• Version bumped — deferred to 8/8 so the stack does not conflict on every restack
• Changelog record added — deferred to 8/8
• Documentation updated (not only docstrings) — covered by the already-merged ADRs
• Fixup commits are squashed away
• Unit tests added/updated
• Manual testing instructions provided
• Noted any: Concerns, dependencies, migration issues, deadlines, tickets — depends on feat: add authz schema policy renderer #479 and the models in feat: add authz schema definition models #478; no migration of its own

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[carlos-marquez-wgu]

LGTM, thanks!

[mariajgrimaldi]

I left a few comments that I think could apply more broadly across the PR, but I didn’t want to repeat the same thing in multiple places. Let me know what you think!

[mariajgrimaldi]

Can we use API methods instead of handling the policy directly?

[mariajgrimaldi]

Is this import in this level necessary?

[mariajgrimaldi]

Same question here about not using casbin methods but instead low-level APIs? So we encapsulate getting the enforcer and so on.

[mariajgrimaldi]

I also don't think we should do the cache invalidation manually