Use 'RUN chown..' to support old Docker versions

Dockerfile

@@ -11,8 +11,6 @@ rm -rf /tmp/* /var/cache/apk/*
 
 WORKDIR /opt/app
 
-USER node
-
 # Install app dependencies
 # A wildcard is used to ensure both package.json AND package-lock.json are copied
 # where available (npm@5+)
@@ -23,7 +21,14 @@ COPY webpack*.js ./
 COPY babel.config.js ./
 
 # Bundle app source
-COPY --chown=node src ./src
+COPY src ./src
+
+# If translations are fetched from Google Sheets API, 
+# the 'node' user needs to be able to write into this folder
+RUN chown -R node:node ./src/client/translations
+
+# https://github.com/nodejs/docker-node/blob/main/docs/BestPractices.md#non-root-user
+USER node
 
 # Run the scripts defined in package.json
 RUN npm install && \