fix: look up request country code without storing it in the session

[blarghmatey]

Description

CountryMiddleware stored country_code and ip_address in the session whenever the client IP was globally routable and differed from the stored ip_address. For a request without a session cookie that condition is always true, so every such response created a new session and carried a Set-Cookie. That includes responses that have no other use for a session, such as course assets served by contentserver, and it adds a session-store write per request from cookie-less clients.

On an LMS behind a CDN we observed this directly: repeated cookie-less requests for a public course asset each returned a different new session cookie.

This PR removes the middleware and adds geoinfo.api.country_code_for_request(request), which the two consumers of the session value now call:

• lms/djangoapps/courseware/block_render.py (user_location, passed to the user service as request_country_code; the video block uses it to choose VIDEO_CDN_URL)
• openedx/core/djangoapps/catalog/utils.py (get_localized_price_text)

The lookup is memoized on the request object and never reads or writes the session. Embargo and registration already call country_code_from_ip directly and are unchanged.

Implications for operators:

• openedx.core.djangoapps.geoinfo.middleware.CountryMiddleware no longer exists. Deployments that list it in a custom MIDDLEWARE setting need to drop it.
• The GeoIP lookup now runs once per request that renders blocks (or localizes a price), instead of once per IP change per session. Stale country_code/ip_address keys in existing sessions are ignored.

Testing instructions

• pytest openedx/core/djangoapps/geoinfo/tests/test_api.py openedx/core/djangoapps/catalog/tests/test_utils.py::TestGetLocalizedPriceText --ds=lms.envs.test passes locally (8 tests). The new tests cover IPv4/IPv6 lookups, skipping non-global IPs, memoization, and that the session stays empty and unmodified.
• ruff check passes on the changed files.
• Not run locally: the courseware block render tests, which need MongoDB.
• Manual: with no session cookie, request a public course asset from the LMS (curl -D - <lms>/asset-v1:...) and confirm the response has no session Set-Cookie.

🤖 Generated with Claude Code

https://claude.ai/code/session_019Sz2VhptEzudj4pimSv1bF

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