feat(ns-plug): dual-send backup to my-new proxy

Adds a second upload to https://my.nethesis.it/proxy/backup after
remote-backup finishes its upload to backupd.nethesis.it. Same
transitional pattern already used by send-heartbeat and send-inventory:
the proxy accepts the existing system_id:secret Basic Auth pair and
translates it into the my-new system_key:system_secret on its way to
the new collect endpoint, so no UCI or registration change is needed
on the appliance.

Gated to enterprise subscriptions via `TYPE = enterprise` to stay in
sync with the other dual-send scripts. Best-effort (`|| :`): a proxy
outage does not block the primary upload that already completed
against backupd, and the md5 marker is still updated so the same
backup is not re-uploaded the next night.

X-Filename is propagated so the user-facing filename ends up as S3
object metadata on my-new.

Refs: NethServer/my#82 NethServer/my#83

Author: edospadoni

packages/ns-plug/files/remote-backup

@@ -54,6 +54,17 @@ case "$cmd" in
            exit_error "No file specified"
        fi
        curl $curl_args $base_url --upload-file $file
+       rc=$?
+       # Temporary dual-send to new my.nethesis.it via the translation
+       # proxy, same pattern used by send-heartbeat / send-inventory.
+       # To be removed once the migration is complete.
+       if [ "$TYPE" = "enterprise" ]; then
+           curl $curl_args -X POST \
+               -H "Content-Type: application/octet-stream" \
+               -H "X-Filename: $(basename "$file")" \
+               --data-binary "@$file" https://my.nethesis.it/proxy/backup >/dev/null || :
+       fi
+       exit $rc
        ;;
    delete)
        file=$2