build: bump jdk to 21 and spring-boot to 3.2.0

[paul58914080]

Checklist for self review:

• [x] My code follows the contribution guidelines of this project
• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [x] My commits follow conventional commit message guidelines

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (0e48dad) 87.80% compared to head (4c50569) 87.80%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #412 +/- ## ========================================= Coverage 87.80% 87.80% Complexity 202 202 ========================================= Files 51 51 Lines 533 533 Branches 22 22 ========================================= Hits 468 468 Misses 51 51 Partials 14 14 ```

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