fix: sync block structure cache before building navigation sidebar

[BryanttV]

Description

This PR fixes stale content in the Learning MFE left navigation sidebar after course publish (e.g., content group visibility changes in Studio OR updates in the block names).

On sidebar cache miss, synchronously refresh the block structure cache before building the outline tree, so the sidebar is not populated from outdated block structure data while the async Celery task is still pending.

Problem

After publishing course changes in Studio, the Learning MFE sidebar (GET /api/course_home/v1/navigation/{course_key}) can show outdated blocks for up to one hour.

Root cause

The navigation endpoint caches the intermediate outline tree for one hour, keyed in part by course_version (the published structure version_guid).

When a course is published:

1. course_version changes > sidebar cache miss (new cache key).
2. The view rebuilds the tree via get_course_outline_block_tree > get_blocks > get_collected().
3. get_collected() can return stale block structure from cache because it does not re-check freshness on a cache hit.
4. Block structure is updated asynchronously by Celery (update_course_in_cache_v2), with a 30-second delay after course_published (BLOCK_STRUCTURES_SETTINGS['COURSE_PUBLISH_TASK_DELAY']).

If the sidebar is requested in that window, stale block structure is cached under the new course_version key for one hour, even though Celery later updates block structure correctly.

Solution

On sidebar cache miss, call update_course_in_cache(course_key) synchronously before building the outline tree. This uses the existing update_collected_if_needed() path, which refreshes the block structure only when it is outdated.

Supporting information

• [Test failure] TC-00058: Restricted Content Visibility by Cohort wg-build-test-release#600

Testing instructions

Using Tutor local:

1. From Studio, create a course and create two content groups (Content Group A and Content Group B).
2. From the LMS, create 2 cohorts, each linked to a Content Group.
3. Assign a user to a cohort.
4. Create two or more units.
5. Modify the visibility of the one unit so that it is restricted only to Content Group A.
6. Modify the visibility of the other unit so that it is restricted only to Content Group B.
7. Make changes by modifying the visibility of the units and immediately (before 30 seconds pass), as a student, verify that the sidebar is correctly updated.

Deadline

Verawood

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