[backend] Improve hub/children synchronization pattern (#6253)

[SamuelHassine]

Proposed changes

Related issues

Checklist

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

Further comments

If this is a relatively large or complex change, kick off the discussion by explaining why you chose the solution you did and what alternatives you considered, etc...

[codecov]

Codecov Report

Attention: Patch coverage is 55.17241% with 26 lines in your changes are missing coverage. Please review.

Project coverage is 66.66%. Comparing base (853ae73) to head (3661825).

Files	Patch %	Lines
...latform/opencti-graphql/src/database/middleware.js	71.42%	12 Missing ⚠️
...latform/opencti-graphql/src/manager/syncManager.js	0.00%	11 Missing ⚠️
...tform/opencti-graphql/src/database/file-storage.js	50.00%	1 Missing ⚠️
...i-platform/opencti-graphql/src/domain/connector.js	0.00%	1 Missing ⚠️
...ti-platform/opencti-graphql/src/graphql/graphql.js	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #6254   +/-   ##
=======================================
  Coverage   66.66%   66.66%           
=======================================
  Files         541      541           
  Lines       64408    64421   +13     
  Branches     5251     5256    +5     
=======================================
+ Hits        42936    42946   +10     
- Misses      21472    21475    +3     

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