fix(sentry-FLAGSMITH-API-4BN): update permission method

[gagantrivedi]

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Changes

Update get_permitted_environments on APIKeyUser to add support for prefetch_metadata
Fixes: FLAGSMITH-API-4BN

How did you test this code?

Adds/updates unit tests

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Name	Status	Preview	Comments	Updated (UTC)
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[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.87%. Comparing base (73d1f91) to head (f8179e0).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3851      +/-   ##
==========================================
- Coverage   95.87%   95.87%   -0.01%     
==========================================
  Files        1129     1129              
  Lines       35788    35787       -1     
==========================================
- Hits        34310    34309       -1     
  Misses       1478     1478              

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[zachaysan]

The code looks good, but consider using the new fixture that I've mentioned in this PR since I think the plan will be to replace all occurrences with that fixture where possible.