feat(event_bus): add document.entered_folder event type and payload schema

surfsense_backend/app/event_bus/events/__init__.py

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+"""Domain event type definitions — each in its own module, self-registering at import."""
+
+from __future__ import annotations
+
+from . import document_entered_folder  # noqa: F401

surfsense_backend/app/event_bus/events/document_entered_folder.py

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+"""``document.entered_folder``: a document became a member of a folder.
+
+Fires once per arrival, however the document got there (upload, AI sort, move).
+The payload carries the fields a user can filter a trigger on.
+"""
+
+from __future__ import annotations
+
+from pydantic import BaseModel, ConfigDict, computed_field
+
+from app.event_bus.catalog import EventType, catalog
+
+EVENT_TYPE = "document.entered_folder"
+
+
+class DocumentEnteredFolderPayload(BaseModel):
+    """Snapshot of the document at the moment it entered ``folder_id``.
+
+    ``previous_folder_id`` is the folder it left, or ``None`` for a first
+    placement. ``is_move`` derives from it and is emitted for filtering.
+    """
+
+    model_config = ConfigDict(extra="forbid")
+
+    document_id: int
+    folder_id: int
+    previous_folder_id: int | None = None
+    document_type: str
+    title: str
+    connector_id: int | None = None
+    created_by_id: str | None = None
+
+    @computed_field
+    @property
+    def is_move(self) -> bool:
+        return self.previous_folder_id is not None
+
+
+catalog.register(
+    EventType(
+        type=EVENT_TYPE,
+        description="A document became a member of a folder.",
+        payload_model=DocumentEnteredFolderPayload,
+    )
+)
+
+
+def payload_if_entered_folder(
+    *,
+    document_id: int,
+    search_space_id: int,
+    new_folder_id: int | None,
+    previous_folder_id: int | None,
+    folder_id_changed: bool,
+    status_state: str,
+    document_type: str,
+    title: str,
+    connector_id: int | None,
+    created_by_id: str | None,
+) -> dict | None:
+    """Return a publish payload if this commit represents a folder arrival, else None.
+
+    ``folder_id_changed`` comes from SQLAlchemy attribute history — it is True
+    only when ``folder_id`` actually changed in this transaction, preventing
+    spurious events on unrelated saves.
+    """
+    if not folder_id_changed:
+        return None
+    if new_folder_id is None:
+        return None
+    if status_state != "ready":
+        return None
+
+    return {
+        "event_type": EVENT_TYPE,
+        "search_space_id": search_space_id,
+        "payload": {
+            "document_id": document_id,
+            "folder_id": new_folder_id,
+            "previous_folder_id": previous_folder_id,
+            "document_type": document_type,
+            "title": title,
+            "connector_id": connector_id,
+            "created_by_id": created_by_id,
+        },
+    }

surfsense_backend/tests/unit/event_bus/test_document_entered_folder.py

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+"""``document.entered_folder`` payload contract + catalog registration."""
+
+from __future__ import annotations
+
+import pytest
+
+from app.event_bus.catalog import catalog
+from app.event_bus.events.document_entered_folder import (
+    EVENT_TYPE,
+    DocumentEnteredFolderPayload,
+)
+
+pytestmark = pytest.mark.unit
+
+
+def _payload(**overrides: object) -> DocumentEnteredFolderPayload:
+    base: dict[str, object] = {
+        "document_id": 42,
+        "folder_id": 7,
+        "document_type": "FILE",
+        "title": "Q3 report.pdf",
+    }
+    base.update(overrides)
+    return DocumentEnteredFolderPayload(**base)
+
+
+def test_payload_carries_the_filterable_fields() -> None:
+    payload = _payload(connector_id=12, created_by_id="abc")
+
+    assert payload.document_id == 42
+    assert payload.folder_id == 7
+    assert payload.document_type == "FILE"
+    assert payload.connector_id == 12
+
+
+def test_first_placement_is_not_a_move() -> None:
+    """No previous folder (created or AI-sorted into place) → not a move."""
+    assert _payload(previous_folder_id=None).is_move is False
+
+
+def test_change_between_folders_is_a_move() -> None:
+    assert _payload(previous_folder_id=3).is_move is True
+
+
+def test_is_move_is_serialized_for_filtering() -> None:
+    """Filters match against the dumped payload, so ``is_move`` must appear there."""
+    dumped = _payload(previous_folder_id=3).model_dump()
+
+    assert dumped["is_move"] is True
+
+
+def test_event_type_is_registered_in_the_catalog() -> None:
+    registered = catalog.get(EVENT_TYPE)
+
+    assert registered is not None
+    assert registered.payload_model is DocumentEnteredFolderPayload