[Fixes #12326] Assets: implement migration for old uploaded files

[mattiagiupponi]

Checklist

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[codecov]

Codecov Report

Attention: Patch coverage is 0% with 74 lines in your changes missing coverage. Please review.

Project coverage is 64.26%. Comparing base (51458d5) to head (395022d).

Additional details and impacted files

@@                Coverage Diff                @@
##           assets_master   #12364      +/-   ##
=================================================
- Coverage          64.35%   64.26%   -0.09%     
=================================================
  Files                885      886       +1     
  Lines              53076    53150      +74     
  Branches            6548     6560      +12     
=================================================
  Hits               34155    34155              
- Misses             17408    17482      +74     
  Partials            1513     1513