"sftp" is not supported as backend for docker volume?

[rnwolf]

Describe the bug

Backup of Docker volume to sftp backend is not working.

Expected behavior

Backup to local drive works.
Expected the same for sft backend.
Are able to backup files from local "home" location to "remote" backend.

Environment

NAME="Ubuntu"
VERSION_ID="22.04"
VERSION="22.04.5 LTS (Jammy Jellyfish)"
VERSION_CODENAME=jammy
autorestic version 1.8.3
restic version : restic 0.17.3 compiled with go1.23.3 on linux/amd64

Additional context

Terminal output

root@mail:~# autorestic backup -l docker_volumes -c ./.autorestic.yml
Using config:    /root/.autorestic.yml
Using lock:      .autorestic.lock.yml

Backing up location "docker_volumes"

Backend: hdd
Backend: remote

docker_volumes@remote:
Backend type "sftp" is not supported as volume endpoint

Error: 1 errors were found

.autorestic.yml

version: 2

backends:
    remote:
        key: XXXXXXXXXXXX
        path: backup:restic-repo
        type: sftp
    hdd:
        type: local
        path: /root/my_server_storage
        key: mysecretkey

locations:

    docker_volumes:
        from:
          - mailcowdockerized_vmail-vol-1
        type: volume
        to:
          - hdd
          - remote

    home:
        #cron: 0 0 * * MON
        from: /root/test
        to: remote

[rnwolf]

If I comment out the remote backend for docker_volumes to backup to local hdd works file.
Backup from local home to remote also works ok.

root@mail:~# autorestic backup -l docker_volumes -c ./.autorestic.yml
Using config:    /root/.autorestic.yml
Using lock:      .autorestic.lock.yml
Backing up location "docker_volumes"
Backend: hdd
Done

root@mail:~# autorestic backup -l home -c ./.autorestic.yml
Using config:    /root/.autorestic.yml
Using lock:      .autorestic.lock.yml
Backing up location "home"
Backend: remote
Done