feat: optimize Docker image with custom JRE and minimal base

- Create custom JRE with jlink using only required modules
- Use debian:bookworm-slim with security updates
- Remove unnecessary files to reduce image size

Author: mkjsix

core/Dockerfile

@@ -1,5 +1,20 @@
-ARG ECLIPSE_TEMURIN_JRE=21-jre
-FROM eclipse-temurin:${ECLIPSE_TEMURIN_JRE}
+FROM eclipse-temurin:21 AS jre-build
+
+# Create a custom Java runtime
+RUN $JAVA_HOME/bin/jlink \
+         --add-modules java.base,java.compiler,java.desktop,java.management,java.naming,java.security.jgss,java.security.sasl,java.sql,jdk.unsupported \
+         --strip-debug \
+         --no-man-pages \
+         --no-header-files \
+         --compress=zip-6 \
+         --output /javaruntime
+
+# Define the base image
+FROM debian:bookworm-slim
+
+ENV JAVA_HOME=/opt/java/openjdk
+ENV PATH="${JAVA_HOME}/bin:${PATH}"
+COPY --from=jre-build /javaruntime $JAVA_HOME
 
 LABEL org.opencontainers.image.title="RESTHeart"
 LABEL org.opencontainers.image.description="RESTHeart is Java Framework, built on top of Undertow"
@@ -14,8 +29,13 @@ LABEL maintainer="SoftInstigate <info@softinstigate.com>"
 # Reduce image size by removing package lists after installation
 RUN apt-get update && \
     apt-get upgrade -y && \
+    apt-get install -y --no-install-recommends ca-certificates && \
+    apt-get autoremove -y && \
     apt-get clean && \
-    rm -rf /var/lib/apt/lists/*
+    rm -rf /var/lib/apt/lists/* && \
+    rm -rf /tmp/* && \
+    rm -rf /var/tmp/* && \
+    rm -rf /var/cache/apt/archives/*
 
 WORKDIR /opt/restheart
 
@@ -29,4 +49,5 @@ COPY target/plugins/lib/*.jar plugins/lib/
 ENV RHO='/mclient/connection-string->"mongodb://host.docker.internal";/http-listener/host->"0.0.0.0"'
 
 ENTRYPOINT [ "java", "-Dfile.encoding=UTF-8", "-server", "-jar", "restheart.jar" ]
+
 EXPOSE 8009 8080 4443