refactor(storage-box): simplify tests

[lukasmetzner]

• remove redundant parsing of full storage box properties
• make tests more coherent between storage box and the subressources snapshot and subaccount

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.39%. Comparing base (9694b91) to head (6b9e007).
⚠️ Report is 1 commits behind head on sbx-api-changes.

Additional details and impacted files

@@                 Coverage Diff                 @@
##           sbx-api-changes     #746      +/-   ##
===================================================
- Coverage            78.42%   78.39%   -0.04%     
===================================================
  Files                   59       59              
  Lines                 5600     5600              
===================================================
- Hits                  4392     4390       -2     
- Misses                 915      917       +2     
  Partials               293      293              

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