feat: integrate relation extraction

[SoniaBadene]

Proposed changes

• Updated webservice call to use /extract_entities_relations endpoint with with_relations=true param.
• Extended parsing logic to handle relationships from ML model response.
• Tracked text-to-STIX ID mapping for relationship linking.
• Added support for Identity types (Sector, Organization, Individual) and custom object Channel.
• Created STIX relationships dynamically from predicted data when valid source/target IDs are found.
• Preserved original fallback logic for known relationship rules (simplified the code).

TODO:

• [ ] for perf, maybe avoid creating duplicate Relationship objects (rel_type, src_id, dst_id), so to have fewer instantiated Python objects, and if we need for later (text highlights) keep every textual mention by enriching the bundle with Note/Observed-Data ..

Related issues

• #3986

[gregoirelafay]

There is a typing issue related to self.file being implicitly defined as None in the __init__. We should initialize it there with self.file: dict[str, Any] | None = None

[flavienSindou]

During my review and tests, I encountered several configuration issues (entirely due to my own setup...), and unfortunately the container did not log any errors to stdout, only a generic "Terminated" message. I’d like to suggest, at least, updating main.py to display the full traceback upon failure, similar to the approach used in other connectors within the codebase

main.py:

# -*- coding: utf-8 -*-
"""OpenCTI ReportImporter connector main module."""

from reportimporter import ReportImporter

if __name__ == "__main__":
    import traceback
    try:
        connector = ReportImporter()
        connector.start()
    except Exception:
        traceback.print_exc()
        exit(1)