BUG: Documentation is missing adding schema folder to ingest-file

[lu-kalk]

Describe the bug
The documentation on customizing the data model instructs you to add the schema folder to api and worker services in docker-compose.yml. But it also needs to be added to ingest-file and mounted when running aleph upgrade.

Expected behavior

### Mount a volume

If you deploy Aleph using Docker Compose, this is the most straight-forward approach.

<Steps>
  <Step>
    Add a separate item to the `volumes` configuration of the `api` and `worker` service in `docker-compose.yml` as shown below. This will make the contents of the `my-custom-schema` directory available inside of the Docker container at `/usr/local/my-custom-schema`.

    ```yaml title="docker-compose.yml"
    api:
      # ...
      volumes:
        # ...
        - ./my-custom-schema:/usr/local/my-custom-schema # Append this line

    worker:
      # ...
      volumes:
        # ...
        - ./my-custom-schema:/usr/local/my-custom-schema # Append this line

    ingest-file:
      # ...
      volumes:
        # ...
        - ./my-custom-schema:/usr/local/my-custom-schema # Append this line
    ```
  </Step>

  <Step>
    Set the `FTM_MODEL_PATH` configuration option to point to the directory that contains your custom model, for example `/usr/local/my-custom-schema`.
  </Step>

  <Step>
    Apply the changes:

    ```sh
    docker compose -d up
    ```
  </Step>

  <Step>
    When you upgrade aleph, make sure to mount the volume aswell:

    ```sh
    docker compose run --volume <path-to-schema>:/usr/local/my-custom-schema --rm shell aleph upgrade
    ```
  </Step>
</Steps>

Aleph version

Screenshots

Additional context
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