fix: restructure can_redeem to gracefully handle error

[kiram15]

Description:
models.py: Separate the get_content_metadata fetch into its own try/except, catching HTTPError and raising ContentPriceNullException instead. This normalizes the exception type for all callers.

subsidy_access_policy.py: The original single try/except ContentPriceNullException block covered all three branches (resolved_policy, successful_redemptions, else) and always raised a RedemptionRequestException on failure. For a learner who has already redeemed, a missing catalog entry is a data/catalog mismatch that should not fail the request.

Jira:
ENT-11649

Merge checklist:

• ./manage.py makemigrations has been run
  • Note: This must be run if you modified any models.
    • It may or may not make a migration depending on exactly what you modified, but it should still be run.

Post merge:

• Ensure that your changes went out to the stage instance
• Deploy to prod instance

[Copilot]

Pull request overview

This PR restructures list-price fetching and error handling so can_redeem can treat missing catalog/metadata differently depending on whether the learner can redeem vs has already redeemed.

Changes:

• SubsidyAccessPolicy.get_list_price now wraps HTTPError from content-metadata fetch as ContentPriceNullException.
• can_redeem now uses separate error-handling paths for resolved_policy, successful_redemptions, and the non-redeemable/no-redemption case, avoiding request failure for already-redeemed content with missing catalog entries.
• Adds warning logging for the already-redeemed + missing price scenario.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
enterprise_access/apps/subsidy_access_policy/models.py	Normalizes metadata-fetch HTTP failures into ContentPriceNullException for list-price computation.
enterprise_access/apps/api/v1/views/subsidy_access_policy.py	Refactors can_redeem list-price logic to avoid failing requests for already-redeemed content when metadata is missing.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.26%. Comparing base (dfdeddf) to head (38aee72).
⚠️ Report is 74 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #108      +/-   ##
==========================================
+ Coverage   84.01%   86.26%   +2.24%     
==========================================
  Files         144      153       +9     
  Lines       12226    12670     +444     
  Branches     1170     1211      +41     
==========================================
+ Hits        10272    10930     +658     
+ Misses       1625     1425     -200     
+ Partials      329      315      -14     

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[brobro10000]

Once its merged, validate down stream consumers (course about page) is still receiving the expected messaging related to subsidy type, and catalog inclusion 👍🏽 . I would wait for either @pwnage101 or @iloveagent57 for final approval, but looks good on my end.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.