Endpoint to update an existing context by its ID.
Args: context_id (str): The unique identifier of the context to update. context_update (ContextCreate): The updated context data.
Returns: dict: A confirmation message indicating the update was successful.
Raises: HTTPException 404: If the context with the given ID does not exist. HTTPException 500: If a runtime error occurs during the update process.
JWT Authorization header using the Bearer scheme. Example: 'Authorization: Bearer {token}'
Successful Response