Improve docker setup

- add .dockerignore to minimize build context
- add runtime ldap and sasl libraries
- add entrypoint script to allow initialization as root and drop
  privileges for gvaldap.sh
- add importlib-metadata dependency required by celery

Dockerfile

@@ -41,6 +41,8 @@ RUN apt-get update \
        ca-certificates \
        dumb-init \
        gettext \
+       libldap-2.4-2 \
+       libsasl2-2 \
        python3 \
        python3-pip \
        python3-wheel \
@@ -59,10 +61,8 @@ RUN addgroup --gid $GVAGID $GVAAPP ; \
 
 COPY --chown=$GVAAPP:$GVAAPP --from=builder /srv/$GVAAPP/.venv /srv/$GVAAPP/.venv
 
-USER $GVAAPP
+VOLUME /srv/$GVAAPP/$GVAAPP
 
-VOLUME /srv/$GVAAPP
+COPY ${GVAAPP}.sh entrypoint.sh /srv/
 
-COPY ${GVAAPP}.sh /srv/
-
-ENTRYPOINT ["dumb-init", "/srv/${GVAAPP}.sh"]
+ENTRYPOINT ["dumb-init", "/srv/entrypoint.sh"]