Adding docker entry for backend

This allow you to run `docker-compose up` in the backend directory
to run the whole backend in a docker. by default the port is set to 4000

backend/Dockerfile

@@ -0,0 +1,4 @@
+FROM eclipse-temurin:21-jdk-alpine
+VOLUME /tmp
+COPY build/libs/backend-0.0.1-SNAPSHOT.jar /app.jar
+ENTRYPOINT ["java", "-jar", "/app.jar"]

backend/compose.yaml

@@ -1,4 +1,8 @@
 services:
+  backend:
+    build: .
+    ports:
+      - 4000:8080
   postgres:
     image: 'postgres:latest'
     environment: