Error codes - Connector API

HTTP	Description
`400`	Missing `Client-Id`; session not initialized; unknown entity; invalid `date_from`; no entities for `start-upload`
`401`	Invalid or missing token (`User not authenticated`)
`403`	`upload_uuid` does not match active session (`Invalid upload UUID`); disallowed IP
`404`	Session record not found (`GET /status`); workflow not running or Connector not found (`terminate`)
`409`	See 409 conflict formats below
`413`	Request body too large
`422`	Invalid request body (Pydantic) or invalid ingest payload (string `detail`)
`500`	Connector or internal error (status may be forwarded from Connector)
`502`	Cannot connect to Connector service
`503`	Rate limit or connection limit exceeded

Full per-endpoint bodies: API responses.

{
  "detail": {
    "message": "Invalid upload session status",
    "expected": "UPLOADING",
    "actual": "DONE"
  }
}

HTTP status: 409 Conflict. For a DONE session, call initialize-session to start a new upload cycle.

409 uses three different body shapes depending on the endpoint: 1. POST /initialize-session — flat object (no detail wrapper):

{
  "status": "already_exists",
  "session_status": "UPLOADING",
  "upload_uuid": "...",
  "message": "Upload session already exists"
}

2. Wrong session status (delete, ingest, start-upload when not UPLOADING) — structured detail:

{
  "detail": {
    "message": "Invalid upload session status",
    "expected": "UPLOADING",
    "actual": "STARTED"
  }
}

3. Pending background tasks (start-upload only) — string detail:

{"detail": "Upload tasks are still in progress"}