Update Dockerfile (#58)

Dockerfile

@@ -1,5 +1,14 @@
-FROM eclipse-temurin:17.0.7_7-jre
-WORKDIR /application
-RUN rm -rf /application
-ADD target/*.jar /application/app.jar
-ENTRYPOINT ["java", "-jar",  "/application/app.jar"]
+FROM eclipse-temurin:21.0.2_13-jre-alpine
+
+WORKDIR /opt/app/
+COPY ./target/*.jar /opt/app/app.jar
+
+# Setup a non-root user context (security)
+RUN addgroup -g 1000 tomcatgroup
+RUN adduser -D -s / -u 1000 tomcatuser -G tomcatgroup
+RUN mkdir /opt/app/temp-files
+RUN chown -R 1000:1000 /opt/app
+
+USER 1000
+
+ENTRYPOINT ["java", "-jar",  "/opt/app/app.jar"]