externalized user and group config from docker image build, config with env...

externalized user and group config from docker image build, config with env USER and GID (of docker group) or build-args AUSER and AGID (of docker group)

Dockerfile

@@ -25,22 +25,23 @@ ENV SPRING_CONFIG_ADDITIONAL_LOCATION "file:/data/config/"
 COPY --from=corretto-jdk /customjre $JAVA_HOME
 
 # Add app user
-ARG APPLICATION_USER=appuser
-RUN addgroup -g 137 -S docker
-RUN adduser --no-create-home -u 1000 -G docker -D $APPLICATION_USER
+ARG AUSER=appuser
+ARG AGID=137
+ENV USER=$AUSER
+ENV GID=$AGID
+RUN addgroup -g $GID -S docker
+RUN adduser --no-create-home -u 1000 -G docker -D $USER
 
 # Prepare environment.
 # Create needed folders
 RUN mkdir /data && \
     mkdir /data/config && \
-    chown -R $APPLICATION_USER /data
-
-EXPOSE 8080
+    chown -R $USER /data
 
 VOLUME /data
 
-COPY --chown=1000:1000 target/dta-backend.jar app.jar
+COPY --chown=1000:$GID target/dta-backend.jar app.jar
 
-USER 1000
+USER 1000:$GID
 
 ENTRYPOINT ["java","-Djava.security.egd=file:/dev/./urandom","-jar","/app.jar"]