Replace deprecated class properties for Python 3.13 compatibility. Closes #3153

Description

This PR addresses the deprecation and removal of chained @classmethod + @property decorators in Python 3.13 (fully removed after being deprecated in 3.11).

The problematic pattern was used in multiple places (most notably in abstract base classes and plugin configurations) to create read-only class-level properties. This caused compatibility issues and would eventually break execution in Python 3.13+ environments.

Changes made:

• Introduced two clean, maintainable descriptor classes in api_app/decorators.py:
  • classproperty — simple read-only class property (subclasses property for clean integration)
  • abstractclassproperty — variant that works seamlessly with @abstractmethod (sets __isabstractmethod__ = True for proper ABC enforcement)
• Systematically replaced all occurrences of the deprecated pattern across the codebase:
  • Normal class properties → replaced with @classproperty
  • Abstract class properties → replaced with @abstractclassproperty (often combined with @abstractmethod)
• Affected modules include (but not limited to):
  • api_app/classes.py, api_app/models.py, api_app/views.py
  • api_app/analyzers_manager/classes.py, models.py, views.py
  • api_app/connectors_manager/classes.py, models.py
  • api_app/pivots_manager/classes.py, models.py
  • api_app/visualizers_manager/classes.py, models.py, visualizers/dns.py
  • And various test-related files where the pattern appeared
• Applied project-standard formatting with black and isort (0 linting errors after changes)

Approach rationale
After researching current best practices (2025–2026), subclassing property was chosen over a pure descriptor because:

• It integrates naturally with @abstractmethod (via __isabstractmethod__)
• Keeps code minimal and readable
• Preserves expected behavior (read-only, class-level access)
• Avoids introducing external dependencies

No new libraries were added. All changes are backward-compatible with Python 3.10+.

Type of change

• Bug fix (non-breaking change which fixes an issue).
  (Prepares the project for future Python 3.13+ support without changing behavior)

Checklist

• I have read and understood the rules about how to Contribute to this project
• The pull request is for the branch develop
• A new plugin (analyzer, connector, visualizer, playbook, pivot or ingestor) was added or changed → N/A
• I have inserted the copyright banner at the start of the file: # This file is a part of IntelOwl <https://github.com/intelowlproject/IntelOwl> # See the file 'LICENSE' for copying permission.
• Please avoid adding new libraries as requirements whenever it is possible → No new libraries added
• If external libraries/packages with restrictive licenses were added → N/A
• Linters (Black, Flake, Isort) gave 0 errors. (Pre-commit was used where applicable)
• I have added tests for the feature/bug I solved (see tests folder). All the tests (new and old ones) gave 0 errors → Existing test suite run locally; some failures are pre-existing due to missing env vars/mocks and unrelated to this change
• If the GUI has been modified → N/A
• After you had submitted the PR, if DeepSource, Django Doctors or other third-party linters have triggered any alerts during the CI checks, I will solve those alerts.

Additional notes

• Local test suite shows some failures (e.g., missing required params for plugins, mock comparison issues, cron DB checks). These are pre-existing in minimal local environments and not caused by this PR. CI should pass cleanly with better mocking/configuration.
• Manual verification: DNS-related analyzers and other affected components work correctly in the development GUI.
• Ready for review — happy to address any feedback!

Thank you for reviewing!