[backend] update or index internalFile to avoid duplicates (#8235)

[SouadHadjiat]

Proposed changes

• fix elIndexExist
• add tests on existing index
• migration to delete duplicated files (keep the most recent file) : test first if there multiple internal objects indices, if not no need to try to deduplicate.
• to avoid creation of internal files duplication: update file if index already exists, index file if not

Related issues

#8235

[codecov]

Codecov Report

Attention: Patch coverage is 92.59259% with 2 lines in your changes missing coverage. Please review.

Project coverage is 66.19%. Comparing base (695963a) to head (0afb0c0).
Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
...l/src/modules/internal/document/document-domain.ts	71.42%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8299      +/-   ##
==========================================
+ Coverage   66.18%   66.19%   +0.01%     
==========================================
  Files         597      597              
  Lines       60379    60392      +13     
  Branches     6203     6207       +4     
==========================================
+ Hits        39963    39979      +16     
+ Misses      20416    20413       -3     

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[aHenryJard]

Migration tested locally both with 2 indices on internal file and only one. All good.