[backend/frontend] fix(injectorcontracts): don't use entity as DTO (#4879)

[antoinemzs]

Proposed changes

• Remove use of Domain entity as DTO and use a proper DTO instead

Testing Instructions

1. In the manual injector
2. Create a new injector contract => must succeed
3. Modify new contract
4. Add new domain => must be updated OK
5. Modify again
6. Remove or add attack pattern => must be updated again, domains must remain unchanged
7. Start Nuclei injector => creates all CVE-based contracts
8. Start Nuclei injector a second time: all contracts are being updated
9. Start openaev datasets collector: all payloads created OK
10. Start atomic red team collector: all payloads created OK

Related issues

• Closes InjectorContract API: calling updateInjectorContract may result in error 500 #4879

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
• 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

❌ Patch coverage is 90.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 55.18%. Comparing base (60df372) to head (5594637).
⚠️ Report is 5 commits behind head on master.

Files with missing lines	Patch %	Lines
.../main/java/io/openaev/service/InjectorService.java	0.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #4882      +/-   ##
============================================
- Coverage     55.22%   55.18%   -0.04%     
- Complexity     4303     4329      +26     
============================================
  Files           972      975       +3     
  Lines         28900    29031     +131     
  Branches       2119     2130      +11     
============================================
+ Hits          15959    16020      +61     
- Misses        12003    12073      +70     
  Partials        938      938              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.