build: Use JRE instead of JDK for final Docker image

Use Eclipse Temurin JRE 21 instead of JDK 21 in Dockerfile. This means that the final Docker image for the application will be take up less space. The JDK is for development and we do not need to use it for built Docker images. The JRE is all that we need for running the application.

Author: thorlauridsen

docker/Dockerfile

@@ -22,8 +22,8 @@ COPY . .
 # Exclude tests to speed up the build.
 RUN ./gradlew --no-daemon :api:clean :api:build -x test
 
-# Stage 2: Package the application into a runtime image using temurin JDK 21.
-FROM eclipse-temurin:21.0.8_9-jdk
+# Stage 2: Package the application into a runtime image using temurin JRE 21.
+FROM eclipse-temurin:21.0.8_9-jre-jammy
 WORKDIR /app
 
 # Copy the generated jar from the builder stage.