[backend] add external ref files into AI summarize (#8413)

[frapuks]

Proposed changes

• add external ref files in AI summarize

Related issues

• close [AI] "Summaries file"on all files does not always work #8413

Checklist

• I consider the submitted work as finished
• I tested the code for its functionality
• I wrote test cases for the relevant uses case (coverage and e2e)
• I added/update the relevant documentation (either on github or on notion)
• Where necessary I refactored code to improve the overall quality

[codecov]

Codecov Report

Attention: Patch coverage is 7.14286% with 13 lines in your changes missing coverage. Please review.

Project coverage is 66.63%. Comparing base (e083712) to head (c11c054).
Report is 24 commits behind head on master.

Files with missing lines	Patch %	Lines
...atform/opencti-graphql/src/modules/ai/ai-domain.ts	7.14%	13 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8926      +/-   ##
==========================================
+ Coverage   66.30%   66.63%   +0.32%     
==========================================
  Files         597      597              
  Lines       61033    61061      +28     
  Branches     6279     6592     +313     
==========================================
+ Hits        40468    40687     +219     
+ Misses      20565    20374     -191     

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[marieflorescontact]

locally tested ok 👌