Add Docker build and push jobs to GitLab CI pipeline

backend/.gitlab-ci.yml

@@ -1,6 +1,10 @@
 stages:
   - backend_build
 
+variables:
+  REGISTRY: registry.gitlab.com/rheinsw/$CI_PROJECT_PATH
+  TAG: $CI_COMMIT_REF_SLUG
+
 backend_build_job:
   stage: backend_build
   image: maven:3.9.9-eclipse-temurin-21@sha256:2e3824afeb41f61761adee95318814e6669bd59aaf61255b2af47064b8755c02
@@ -14,3 +18,29 @@ backend_build_job:
       - backend/discoveryServer/target/
       - backend/services/**/target
     expire_in: 1 hour
+
+build_shared_base_image:
+  stage: dockerize
+  script:
+    - docker build -f Dockerfile.base -t $REGISTRY/shared-base:$TAG .
+    - docker push $REGISTRY/shared-base:$TAG
+  needs:
+    - backend_build_job
+
+build_gateway_image:
+  stage: dockerize
+  script:
+    - docker build --build-arg JAR_FILE=backend/gateway/target/gateway-*.jar -f Dockerfile.service -t $REGISTRY/gateway:$TAG .
+    - docker push $REGISTRY/gateway:$TAG
+  needs:
+    - backend_build_job
+    - build_shared_base_image
+
+build_discovery_image:
+  stage: dockerize
+  script:
+    - docker build --build-arg JAR_FILE=backend/discoveryServer/target/discoveryServer-*.jar -f Dockerfile.service -t $REGISTRY/discovery-server:$TAG .
+    - docker push $REGISTRY/discovery-server:$TAG
+  needs:
+    - backend_build_job
+    - build_shared_base_image