chore: app user for running container

Dockerfile

@@ -2,6 +2,10 @@
 FROM savonet/liquidsoap:v2.1.0
 LABEL maintainer="David Trattnig <david.trattnig@subsquare.at>"
 
+ENV UID=1000
+ENV GID=1000
+ENV USER=app
+
 USER root
 
 # Dependencies & Utils
@@ -14,13 +18,20 @@ RUN apt update --allow-releaseinfo-change && \
 # Setup Engine
 ENV TZ=Europe/Vienna
 RUN ln -snf /usr/share/zoneinfo/$TZ /etc/localtime && echo $TZ > /etc/timezone
-RUN mkdir -p /srv/src /srv/tests /srv/config srv/logs srv/socket
+RUN mkdir -p /srv/src /srv/tests /srv/config srv/logs srv/socket /var/audio
 COPY src /srv/src
 COPY tests /srv/tests
 COPY config/sample.engine-core.docker.ini /etc/aura/engine-core.ini
 COPY Makefile /srv/Makefile
 COPY VERSION /srv/VERSION
 
+RUN set -e \
+      && adduser --home /srv --no-create-home --system --uid ${UID} --group ${USER} \
+      && chown -R ${UID}:${GID} /srv /var/audio
+RUN
+
+USER app
+
 #RUN chown -R liquidsoap:liquidsoap /srv
 WORKDIR /srv