[BE][edx-platform] Verify Taxonomy Type passes through TaxonomyOrgSerializer #630

Use Case

As a Platform Administrator viewing the Taxonomies page, I want the edx-platform taxonomy API to include taxonomy_type so the page can render the Competency Taxonomy badge and gate access to the Competency Management page, without the frontend calling openedx-tagging directly.

Description

Current behavior

1. The frontend Taxonomies page reads taxonomy data from edx-platform's own endpoint, serialized by TaxonomyOrgSerializer (openedx/core/djangoapps/content_tagging/rest_api/v1/serializers.py:70-99), not from openedx-tagging's /api/tagging/v1/taxonomies/ directly.
2. TaxonomyOrgSerializer(TaxonomySerializer) builds Meta.fields additively: TaxonomySerializer.Meta.fields + ["orgs", "all_orgs"]. This means once [BE] Update Get endpoint to return Taxonomy Type. #618 adds taxonomy_type to the parent's Meta.fields, it is inherited automatically — confirmed by reading the actual class, not assumed.

Requested change

1. Confirm (regression-test, not manual-only) that taxonomy_type appears in TaxonomyOrgSerializer's detail and list responses once [BE] Update Get endpoint to return Taxonomy Type. #618 ships the field, with correct values for a plain and a system-defined taxonomy.
2. No production source change is expected. If investigation at implementation time finds Meta.fields has since been rewritten as an explicit allowlist, patch it to include taxonomy_type.

Depends on: #618 merging first; this ticket verifies the contract #618 defines, it doesn't define its own.

Explicitly out of scope

• No change to openedx-tagging or the CompetencyTaxonomy model.
• No filtering by taxonomy type on this endpoint.
• No frontend badge/gating UI — this ticket only ensures the field reaches the frontend.

Acceptance Criteria

See Acceptance Criteria of parent Github Issue #618.

Technical Details

Files to create and modify

Modified files

Recommended Approach

No source change. Add one or two assertions to the existing TaxonomyOrgSerializer test coverage confirming taxonomy_type appears with correct values, gated on #618 being merged. This converts a one-time manual check into a permanent regression guard against a future contributor rewriting Meta.fields as an explicit allowlist (the more common DRF idiom, and a plausible future refactor that would silently drop the field again).

Example Resolution Prompt

In edx-platform, confirm TaxonomyOrgSerializer (openedx/core/djangoapps/content_tagging/rest_api/v1/serializers.py:70-99) surfaces taxonomy_type once #618 ships it. It is additive (Meta.fields = TaxonomySerializer.Meta.fields + ["orgs", "all_orgs"]), so no source change to serializers.py is expected. Bump the openedx-core pin to a version including the field. Find the existing tests covering TaxonomyOrgSerializer's GET responses (search openedx/core/djangoapps/content_tagging/rest_api/v1/tests/) and add assertions that detail and list responses include "taxonomy_type", with correct values for a plain taxonomy ("tags") and a system-defined taxonomy ("tags", never null). Do not modify Meta.fields, get_orgs, or get_all_orgs unless investigation finds they've since changed to an explicit allowlist.