Add generic JSON import module (generic_json_import)

[adulau]

Motivation

• Provide a generic import module that can fetch a JSON file from an HTTP(S) URL and convert records into MISP objects or attributes.
• Allow flexible mapping by analysing JSON keys/values against the MISP object templates bundled with PyMISP to produce misp_standard output.

Description

• Add a new import module at misp_modules/modules/import_mod/generic_json_import.py that fetches remote JSON, validates URLs, streams with a 20 MB guard, and parses the content.
• Implement template discovery by loading PyMISP object definitions from MISPObject(...).misp_objects_path and heuristically matching flattened JSON records to templates using alias and inferred value-type scoring.
• Emit matched records as MISPObject instances appended to a MISPEvent and optionally create standalone attributes for recognised indicator values that were not mapped to an object.
• Add configurable userConfig options: timeout, max_records, and include_unmapped_attributes, and include unit tests in tests/test_generic_json_import.py covering object mapping and fallback attribute import.

Testing

• python -m compileall -q misp_modules/modules/import_mod/generic_json_import.py tests/test_generic_json_import.py succeeded.
• python -m black --check misp_modules/modules/import_mod/generic_json_import.py tests/test_generic_json_import.py succeeded after formatting.
• pytest -q tests/test_generic_json_import.py passed (new module tests).
• pytest -q tests/test.py::TestModules::test_introspection_module_structure failed due to an existing test-suite issue (an unrelated module misp_modules.modules.export_mod lacks an expected __all__ attribute), not caused by the new module.

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Codex Task