[admin] Add a spec for /admin/orders

[elia]

Summary

Smoke test the orders index page full stack.

Checklist

Check out our PR guidelines for more details.

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• I have written a thorough PR description.
• I have kept my commits small and atomic.
• I have used clear, explanatory commit messages.

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• 📖 I have updated the README to account for my changes.
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• ✅ I have added automated tests to cover my changes.
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[codecov]

Codecov Report

Merging #5382 (1de8533) into nebulab/admin (9aba822) will increase coverage by 0.73%.
The diff coverage is n/a.

@@                Coverage Diff                @@
##           nebulab/admin    #5382      +/-   ##
=================================================
+ Coverage          87.99%   88.72%   +0.73%     
=================================================
  Files                614      614              
  Lines              14911    14841      -70     
=================================================
+ Hits               13121    13168      +47     
+ Misses              1790     1673     -117     

see 2 files with indirect coverage changes

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