Add Dockerfile and CI

.gitlab-ci.yml

+build:
+  stage: build
+  image:
+    name: gcr.io/kaniko-project/executor:debug
+    entrypoint: [""]
+  script:
+    - echo "{\"auths\":{\"$CI_REGISTRY\":{\"username\":\"$CI_REGISTRY_USER\",\"password\":\"$CI_REGISTRY_PASSWORD\"}}}" >/kaniko/.docker/config.json
+    - /kaniko/executor
+      --context "${CI_PROJECT_DIR}"
+      --dockerfile "${CI_PROJECT_DIR}/Dockerfile"
+      --destination "${CI_REGISTRY_IMAGE}:postgres-latest"
+      --destination "${CI_REGISTRY_IMAGE}:postgres-${CI_COMMIT_TAG}"
+  only:
+    - main

Dockerfile

+FROM postgres:16
+
+RUN apt update && apt install -y postgresql-16-pg-rrule
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