[backend] email notification when score degradation

[heditar]

Proposed changes

• Adding the logic to send an email when there is a score degradation
  !!!! -> some tests were not passing and were removed to meet the ETA for this PR, it will be added later to this PR or to another one if already merged

Related issues

• Ability to be alerted on the differences between 2 simulation’s expecations results on my scheduled scenario #2808

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) -> will be done as another PR
• Where necessary I refactored code to improve the overall quality
• For bug fix -> I implemented a test that covers the bug

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 25.45455% with 82 lines in your changes missing coverage. Please review.

Project coverage is 41.01%. Comparing base (d16e93f) to head (656c70d).
Report is 1 commits behind head on release/current.

Files with missing lines	Patch %	Lines
...tion/handler/ScenarioNotificationEventHandler.java	0.00%	46 Missing ⚠️
...a/io/openbas/service/EmailNotificationService.java	0.00%	17 Missing ⚠️
...api/src/main/java/io/openbas/utils/ImageUtils.java	0.00%	8 Missing ⚠️
...va/io/openbas/service/PlatformSettingsService.java	0.00%	6 Missing ⚠️
...src/main/java/io/openbas/config/SessionHelper.java	0.00%	1 Missing and 1 partial ⚠️
...va/io/openbas/service/NotificationRuleService.java	89.47%	0 Missing and 2 partials ⚠️
...openbas/rest/exercise/service/ExerciseService.java	91.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@                  Coverage Diff                  @@
##             release/current    #3036      +/-   ##
=====================================================
- Coverage              41.11%   41.01%   -0.11%     
- Complexity              2305     2306       +1     
=====================================================
  Files                    685      687       +2     
  Lines                  21015    21106      +91     
  Branches                1436     1438       +2     
=====================================================
+ Hits                    8640     8656      +16     
- Misses                 11889    11960      +71     
- Partials                 486      490       +4     

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