Fix write permissions in test/stage env

Author: filippomc

Dockerfile

@@ -36,9 +36,11 @@ WORKDIR $FOLDER
 COPY --chown=1000:1000 requirements.txt requirements.txt
 RUN --mount=type=cache,target=/root/.cache python -m pip install --upgrade pip && pip install -r requirements.txt --prefer-binary
 
-COPY --chown=$NB_UID:1000 . .
+USER $NB_UID
+COPY . .
 COPY --from=jsbuild --chown=$NB_UID:1000 /app webapp
 
+USER root
 
 RUN jupyter nbextension install --py --symlink --sys-prefix jupyter_geppetto
 RUN jupyter nbextension enable --py --sys-prefix jupyter_geppetto