Turnaround: *use* volumes for sharing data

... but use it in the same pod. It seems to be possible to have shared
volumes in the same pod:
https://kubernetes.io/docs/tasks/access-application-cluster/communicate-containers-same-pod-shared-volume/

db-migration-worker/Dockerfile

@@ -10,3 +10,4 @@ RUN apt-get -y install --no-install-recommends openjdk-8-jre openssh-client neo4
  && rm -rf /var/lib/apt/lists/*
 COPY migration ./migration
 COPY migrate.sh /usr/local/bin/migrate
+COPY sync_uploads.sh /usr/local/bin/sync_uploads

db-migration-worker/sync_uploads.sh

@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+set -e
+
+for var in "SSH_USERNAME" "SSH_HOST" "UPLOADS_DIRECTORY"
+do
+  if [[ -z "${!var}" ]]; then
+    echo "${var} is undefined"
+    exit 1
+  fi
+done
+
+rsync --archive --update --verbose ${SSH_USERNAME}@${SSH_HOST}:${UPLOADS_DIRECTORY}/* /uploads/

docker-compose.db-migration.yml

@@ -1,6 +1,9 @@
 version: "3.7"
 
 services:
+  backend:
+    volumes:
+      - uploads:/nitro-backend/public/uploads
   neo4j:
     volumes:
       - mongo-export:/mongo-export
@@ -11,6 +14,7 @@ services:
       context: db-migration-worker
     volumes:
       - mongo-export:/mongo-export
+      - uploads:/uploads
       - ./db-migration-worker/.ssh/:/root/.ssh/
     networks:
       - hc-network
@@ -24,6 +28,8 @@ services:
       - "MONGODB_PASSWORD=${MONGODB_PASSWORD}"
       - "MONGODB_AUTH_DB=${MONGODB_AUTH_DB}"
       - "MONGODB_DATABASE=${MONGODB_DATABASE}"
+      - "UPLOADS_DIRECTORY=${UPLOADS_DIRECTORY}"
 
 volumes:
   mongo-export:
+  uploads: