[backend] Fix mailer / sending emails in the platform

[SamuelHassine]

Proposed changes

[backend] Fix mailer / sending emails in the platform

Related issues

• Simple mailer does not work anymore (testing or notification based) #5773

[SamuelHassine]

Sending email through testing is ok, but sending through normal notification behavior don't....

[codecov]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (8c0f5c8) 64.76% compared to head (0c46db8) 64.76%.
Report is 3 commits behind head on master.

❗ Current head 0c46db8 differs from pull request most recent head c0f8bd1. Consider uploading reports for the commit c0f8bd1 to get more accurate results

Files	Patch %	Lines
...rm/opencti-graphql/src/manager/publisherManager.ts	25.00%	3 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #5780   +/-   ##
=======================================
  Coverage   64.76%   64.76%           
=======================================
  Files         516      516           
  Lines       60973    60973           
  Branches     4870     4870           
=======================================
  Hits        39489    39489           
  Misses      21484    21484           

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