Update Document Categories

Update the categories assigned to a document.

This endpoint replaces all existing categories for a document with the new list provided. Use this to organize and tag documents for easier retrieval.

Args: id: Document ID (path parameter) req: Request body containing the new list of categories

Returns: None (204 No Content on success)

Raises: HTTPException(404): If the document is not found or doesn’t belong to the user

Example: Request:

    PUT /api/v3/documents/doc-xyz789/categories
    Headers: {"Authorization": "Bearer <api_key>"}
    Body:
    {
        "categories": ["financial", "2024-q1", "confidential"]
    }