feat(opencti): new OpenCTI threat-intelligence integration

Add a marketplace integration for the OpenCTI platform (GraphQL API,
compatible with OpenCTI 5.x/6.x), built on the Python pycti client and
run from a remote engine.

26 commands: observables (list/create/delete/field update/add/remove),
indicators (list/create/update/field add/remove, types), incidents
(list/create/delete, types) with an OCSF ingestion mapper, relationships
(list/create/delete), and reference data (organizations, labels, marking
definitions, external references).

- Ingestion: get_incidents to an OCSF finding mapper + an OpenCTI Incident type.
- Auth: user API key (Bearer) via pycti; requires pip install pycti on
  the engine host.
- Scripts are self-contained (INTEGRATION_SECRETS/INTEGRATION_INPUTS in,
  JSON out) following the established marketplace pattern.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

integrations/opencti/scripts/observable_field_remove.py

@@ -0,0 +1,66 @@
+import json, os, sys
+
+S = json.loads(os.environ.get("INTEGRATION_SECRETS", "{}"))
+I = json.loads(os.environ.get("INTEGRATION_INPUTS", "{}"))
+
+
+def out(value):
+    print(json.dumps(value, default=str))
+
+
+def fail(message, **extra):
+    payload = {"error": message}
+    payload.update(extra)
+    print(json.dumps(payload, default=str))
+    sys.exit(1)
+
+
+def as_bool(v):
+    return v if isinstance(v, bool) else str(v).lower() in ("1", "true", "yes")
+
+
+def as_int(v, default=None):
+    try:
+        return int(v)
+    except (TypeError, ValueError):
+        return default
+
+
+def as_list(v):
+    if isinstance(v, list):
+        return v
+    if v in (None, ""):
+        return []
+    return [x.strip() for x in str(v).split(",") if x.strip()]
+
+
+try:
+    from pycti import OpenCTIApiClient
+except ImportError as e:
+    fail("The 'pycti' Python library is required for the OpenCTI integration. "
+         "Install it on the execution host (engine): pip install pycti", detail=str(e))
+
+
+def client():
+    base = str(S.get("base_url", "")).strip().rstrip("/")
+    api_key = S.get("api_key") or (S.get("credentials") or {}).get("password")
+    return OpenCTIApiClient(base, api_key, ssl_verify=not as_bool(S.get("insecure")), log_level="error")
+
+
+field = I.get("field")
+observable_id = I.get("id")
+value = I.get("value")
+
+try:
+    if field == "marking":
+        result = client().stix_cyber_observable.remove_marking_definition(
+            id=observable_id, marking_definition_id=value
+        )
+    elif field == "label":
+        result = client().stix_cyber_observable.remove_label(id=observable_id, label_id=value)
+    else:
+        fail("Invalid field was provided.")
+except Exception as e:
+    fail("Can't remove field from observable in OpenCTI.", detail=str(e))
+
+out({"success": True, "message": "Removed {0}.".format(field)})