[BE] Build Get endpoint for a Competency Rule Profile (scoped to user's permissions)

[jesperhodge]

Blocked by: #613/#641 (data model), and #631's shared scaffolding (RuleProfileSerializer, is_rule_profile_in_use, the rest_api/v1/ package). Also the one-time openedx-platform wiring from #664.

Repo: openedx-core.

Use Case

As a Platform Administrator (or the Manage & Apply Competencies UI on their behalf), I want to fetch the rule profile that applies to a taxonomy — its own taxonomy-scoped profile if one exists, otherwise the system default — so that the UI can display the effective mastery rule and whether it's the inherited default or a taxonomy override.

Description

Current state

No CompetencyRuleProfile API exists. Per the merged ADR, MVP has exactly two profile scopes: the single system-default (seeded, all-null scope) and one taxonomy-scoped profile per taxonomy; org/course are deferred. The frontend needs to show a taxonomy's effective rule, which is the taxonomy-scoped profile when present and the system default otherwise — and must visually distinguish an inherited default from a taxonomy override. This endpoint supplies the data behind that distinction.

Requested change

A read endpoint for rule profiles:

• Get a taxonomy's effective profile: GET /cbe/rest_api/v1/taxonomies/<taxonomy_id>/rule-profile/ → the taxonomy-scoped profile if one exists, else the system default, with a field indicating which (e.g. source: "taxonomy" | "system_default") so the UI can render inherited-vs-overridden without a second call. Include is_in_use.

• Permission: can_change_taxonomy on the referenced taxonomy for the taxonomy route.

Explicitly out of scope

• Create ([BE] Build Create endpoint for a Competency Rule Profile (scoped to user's permissions) #631), Update/Archive ([BE] Build Update / Delete (archive) endpoint for a Competency Rule Profile (scoped to user's permissions) #632).
• Deletability metadata on the response — that ("determine whether each is deletable and include this metadata") is a separate guardrails ticket in UC10 (task 10.4), not this one. Don't add it here.
• Organization/course-scoped profiles (deferred) and their fields.
• A standalone system-default GET endpoint.
• Any UI (6.5).

Acceptance Criteria

Verifiable via Postman.

Scenario: Get a taxonomy's effective profile when it has its own
  Given a taxonomy has a (non-archived) taxonomy-scoped profile, requester has can_change_taxonomy
  When GET /taxonomies/<id>/rule-profile/ is called
  Then the response is 200 with that profile's fields and "source": "taxonomy"

Scenario: Get a taxonomy's effective profile when it has none (falls back to system default)
  Given a taxonomy has no taxonomy-scoped profile (or only an archived one)
  When GET /taxonomies/<id>/rule-profile/ is called
  Then the response returns the system-default rule with "source": "system_default"

Scenario: is_in_use is reported
  Given a profile with at least one assigned CompetencyCriterion that has a StudentCompetencyCriteriaStatus row
  When the profile is fetched
  Then "is_in_use" is true

Scenario: Reject without permission / nonexistent taxonomy
  Given the requester lacks the applicable permission, or the taxonomy_id doesn't resolve to a CompetencyTaxonomy
  Then the response is 403 or 404

Open Questions

• [non-blocking, owner: implementer] source field naming. Confirm the field/values used to signal inherited-default vs. taxonomy-override, so 6.5's UI and this contract match.

Context

• Merged ADR (0002/0003, PR docs: cbe competency rule profile adr amendments #636): system-default identity (all-null scope); one taxonomy-scoped profile per taxonomy; is_in_use per ADR 0003 Decision 4.
• 07-14 meeting: MVP = system + taxonomy; the inherited-vs-overridden visual distinction is a required capability the UI needs data for.
• UC10 task 10.4 (spreadsheet): the separate "is this deletable" metadata work — deliberately NOT in this Get endpoint.
• [BE] Build Create endpoint for a Competency Rule Profile (scoped to user's permissions) #631: shared RuleProfileSerializer, is_rule_profile_in_use, scaffolding, permission reuse.
• src/openedx_tagging/rest_api/v1/views.py (ObjectTagCountsView precedent for a plain-Response read), rules.py/permissions.py for gating.

Technical Notes

Files to Modify

File	Nature
src/openedx_learning/applets/cbe/api.py	add get_system_default_rule_profile() (internal helper only, no dedicated view; query all-null scope, not by scope_code string) and get_effective_rule_profile(competency_taxonomy_id) (taxonomy-scoped if present & non-archived, else system default via the helper above; returns the profile + which source)
src/openedx_learning/applets/cbe/rest_api/v1/views.py	add TaxonomyEffectiveRuleProfileView (GET); reuse RuleProfileSerializer, add source to its output
src/openedx_learning/applets/cbe/rest_api/v1/urls.py	register taxonomies/<int:taxonomy_id>/rule-profile/
.../rest_api/v1/tests/test_views.py, .../tests/test_api.py	get / fallback-to-default / is_in_use / permission tests

Implementation Notes

get_system_default_rule_profile() queries organization_id__isnull=True, course_id__isnull=True, competency_taxonomy_id__isnull=True — never the scope_code string (the ADR marks that column internal-only). It's an internal helper only, no view calls it directly. get_effective_rule_profile(taxonomy_id) returns the taxonomy's non-archived profile if present, else the system default via that helper, tagging the result so the view can emit source. Do not compute or return deletability (UC10.4). Views are thin: resolve via the api.py function, serialize, return; is_in_use via the shared helper.

Example Resolution Prompt

In openedx-core, add a read endpoint for CompetencyRuleProfile (reusing #631's RuleProfileSerializer and is_rule_profile_in_use). Add get_system_default_rule_profile() (internal helper, query the all-null-scope row, not the scope_code string) and get_effective_rule_profile(competency_taxonomy_id) (return the taxonomy's non-archived profile if present, else the system default via that helper, tagged with its source) to applets/cbe/api.py. Add TaxonomyEffectiveRuleProfileView at taxonomies/<int:taxonomy_id>/rule-profile/ (GET, can_change_taxonomy) that returns the effective profile plus a source field ("taxonomy" | "system_default") and is_in_use. No standalone system-default endpoint. Do NOT include deletability metadata (that's UC10.4). Return 200/403/404 per the AC.

[thelmick-unicon]

The discussion period for this ticket is now complete, and we appreciate all the feedback. We'll be moving forward with development based on the current ticket pending final Axim sign-off. That said, the conversation doesn't have to stop. If you still have feedback, please continue to add to this ticket. We'll review anything new and determine whether it fits within the current timeline or makes more sense as its own ticket for future work. Thanks again for helping make this better!

@ormsbee This is now ready for your review, thank you!