[backend] Fix createdBy validation on SDO edit (#6291)

[SouadHadjiat]

Proposed changes

• Fix error "Cannot read properties of undefined (reading '0')" when editing an entity's author

Related issues

• Creation of created-by relatiohship is not protected to target only identity #6291

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

[aHenryJard]

Thanks !

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 66.74%. Comparing base (1a0ae19) to head (9113b2e).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #6332   +/-   ##
=======================================
  Coverage   66.73%   66.74%           
=======================================
  Files         541      541           
  Lines       64529    64529           
  Branches     5306     5306           
=======================================
+ Hits        43066    43068    +2     
+ Misses      21463    21461    -2     

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