feat: add taxonomy_type to the taxonomy Get/List response

[ufedaseyeuconsultant]

Description

TaxonomyOrgSerializer now reports a read-only taxonomy_type on the taxonomy Get/List
response: "competency" if the taxonomy has a related CompetencyTaxonomy row, "tags"
otherwise. Implements the acceptance criteria from #618.

Changes

• TaxonomyOrgSerializer.to_representation(): overridden to inject taxonomy_type into the
  output after super().to_representation(), computed via
  openedx_learning.api.is_competency_taxonomy(). Not a new declared field: TaxonomySerializer
  already declares taxonomy_type as write-only (create-time input, consumed by
  perform_create()), so a same-named SerializerMethodField would have silently replaced it
  and broken taxonomy creation. DRF excludes write-only fields from output entirely, so this
  override adds the key rather than colliding with one.
• TaxonomyOrgView.get_queryset(): adds select_competency_taxonomies() to the existing
  queryset chain, so the per-row is_competency_taxonomy() check on list costs no extra query.
• Neither openedx_tagging's Taxonomy model nor its base TaxonomySerializer change, per
  ADR 0013 (openedx-core).

Tests

Four test methods, one per #618's Given/When/Then scenario: a plain taxonomy's detail response
→ "tags", a competency taxonomy's detail response → "competency", a list of mixed types →
each entry's taxonomy_type correct and none null. One scenario deviates from the ticket text:
it asks for a "system-defined taxonomy" (system_defined=true) case, but system_defined isn't
a field on TaxonomySerializer at all anymore (removed well before this PR) — substituted a
read_only taxonomy instead, asserting taxonomy_type == "tags" and read_only is True.
Re-ran the existing test_list_taxonomy_query_count (assertNumQueries) unchanged: same counts
with and without this change, confirming select_competency_taxonomies()'s join adds no query.

Manual testing instructions

No local openedx-core mount needed: is_competency_taxonomy() / select_competency_taxonomies()
already shipped in the pinned openedx-core==1.4.0 (same release, same PR,
openedx-core#803, as create_competency_taxonomy()). A standard tutor images build openedx-dev
against this branch is enough.

1. Restart Studio on this branch:

   tutor dev restart lms cms
   

2. Auth script (captures cookies/CSRF/JWT so you don't have to copy requests from devtools each
   time; non-default cases can also be driven from the UI):

   COOKIES=/tmp/lms_cookies.txt; rm -f "$COOKIES"
   curl -s -c "$COOKIES" "http://local.openedx.io:8000/login" -o /dev/null
   CSRFTOKEN=$(grep csrftoken "$COOKIES" | awk '{print $NF}')
   curl -s -b "$COOKIES" -c "$COOKIES" -H "X-CSRFToken: $CSRFTOKEN" -H "Referer: http://local.openedx.io:8000/login" --data-urlencode "email=test@test.com" --data-urlencode "password=test" "http://local.openedx.io:8000/api/user/v1/account/login_session/" -o /dev/null -w "login status: %{http_code}\n"
   AUTH_HEADER="Authorization: JWT $(grep "edx-jwt-cookie-header-payload" "$COOKIES" | awk '{print $NF}').$(grep "edx-jwt-cookie-signature" "$COOKIES" | awk '{print $NF}')"
   CMS_URL="http://studio.local.openedx.io:8001"

3. Create one taxonomy of each type to check against:

   curl -s -H "$AUTH_HEADER" -H "Content-Type: application/json" -X POST "$CMS_URL/api/content_tagging/v1/taxonomies/" -d '{"name": "Test Competency", "description": "test", "taxonomy_type": "competency"}'
   curl -s -H "$AUTH_HEADER" -H "Content-Type: application/json" -X POST "$CMS_URL/api/content_tagging/v1/taxonomies/" -d '{"name": "Test Tags", "description": "test", "taxonomy_type": "tags"}'

4. Get each by id — expect "taxonomy_type": "competency" and "taxonomy_type": "tags"
   respectively:

   curl -s -H "$AUTH_HEADER" "$CMS_URL/api/content_tagging/v1/taxonomies/<competency_id>/"
   curl -s -H "$AUTH_HEADER" "$CMS_URL/api/content_tagging/v1/taxonomies/<tags_id>/"

5. List — expect both entries present, each with the correct taxonomy_type, neither null:

   curl -s -H "$AUTH_HEADER" "$CMS_URL/api/content_tagging/v1/taxonomies/"

6. Confirm in MySQL that a CompetencyTaxonomy row exists for the competency taxonomy's id and
   not for the tags one.

Related to: ADR 0013 (openedx-core)

🤖 Generated with help of Claude Code

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[mgwozdz-unicon]

This looks good! One thing: Please update the links in your description for "#618" to point to openedx/openedx-core#618. Since this is the openedx-platform repo, it defaults "#618" to point at PR #618 for this repo instead of Github Issue #618 from the repo that houses our CBE Github Project.